diff --git a/src/main/java/component/SignatureInfo.java b/src/main/java/component/SignatureInfo.java
index 19a863a..64b7ded 100644
--- a/src/main/java/component/SignatureInfo.java
+++ b/src/main/java/component/SignatureInfo.java
@@ -155,7 +155,13 @@ public class SignatureInfo implements TlvComponentBase, IEncodingAble {
         int elementSize=block.getSubElements().length();
         for (int i=0;i<elementSize;i++) {
             Block cacheBlock=block.getSubElements().getBlock(i);
-            switch (cacheBlock.getType().getVlIntValue2Int()){
+            int type= 0;
+            try {
+                type = cacheBlock.getType().getVlIntValue2Int();
+            } catch (VlIntException e) {
+                e.printStackTrace();
+            }
+            switch (type){
                 case TLV.TlvSignatureType:
                     if(!this.signatureType.wireDecode(cacheBlock)){
                         return false;
diff --git a/src/main/java/encoding/SizeT.java b/src/main/java/encoding/SizeT.java
index 264e345..bc20341 100644
--- a/src/main/java/encoding/SizeT.java
+++ b/src/main/java/encoding/SizeT.java
@@ -45,6 +45,10 @@ public class SizeT {
 
     //todo:判断biginteger是否合法
 
+    public boolean isInitial(){
+        return true;
+    }
+
     public SizeT(byte[] bytes){
         this.VlIntBytes=bytes;
         this.VlIntValue=vlintBytes2bigInteger(bytes);
diff --git a/src/main/java/encoding/VlInt.java b/src/main/java/encoding/VlInt.java
index d44534a..3da790a 100644
--- a/src/main/java/encoding/VlInt.java
+++ b/src/main/java/encoding/VlInt.java
@@ -15,14 +15,13 @@ import static java.lang.Math.pow;
  * @Date: 18:13 2021/3/1
  * @Copyright: MIN-Group；国家重大科技基础设施——未来网络北大实验室；深圳市信息论与未来网络重点实验室
  */
-
 public class VlInt {
     // 实际传输的数据
     private byte[] VlIntBytes;
     // 变长整数表示的真实数值
     private BigInteger VlIntValue;
-    // 变长整数的长度: 1 3 5 9 ...
-    private int size;
+    // 变长整数的长度: 1 3 5 9 ...; 可以通过它来判断是否已经初始化VlInt
+    private int size=-1;
 
     // 一些int常量
     // @Description:
@@ -48,6 +47,9 @@ public class VlInt {
         return this.size;
     }
     private static int SizeOfVarNumber(BigInteger bigInteger){
+        if(bigInteger==null){
+            throw new Error("VlInt.SizeOfVarNumber: VlInt value is null.");
+        }
         if(bigInteger.compareTo(BigInteger.valueOf(241)) < 0){
             return 1;
         }else if(bigInteger.compareTo(BigInteger.valueOf(
@@ -56,33 +58,98 @@ public class VlInt {
         }else if(bigInteger.compareTo(BigInteger.valueOf(
                 new Double(pow(2, 32)).longValue())) < 0){
             return 5;
-        }else{  //MIN1.0中，VlInt的size最大为9
+        }else if(bigInteger.compareTo(BigInteger.valueOf(
+                new Double(pow(2, 64)).longValue())) < 0){
             return 9;
+        }else{
+            //MIN1.0中，VlInt的size最大为9
+            throw new Error("VlInt.SizeOfVarNumber: VlInt value is out of bound, it should be less than 2^64.");
         }
     }
 
-    //todo:判断bytes是否是一个合法的变长非负整型
-    private boolean isValidVlIntBytes(){
+    /**
+     * 判断bytes是否是一个合法的变长非负整型
+     * @param vlIntBytes
+     * @return
+     */
+    private boolean isValidVlIntBytes(byte[] vlIntBytes){
+        if(vlIntBytes.length<1){
+            return false;
+        }
+        int firstByteValue=ByteHelper.uint8ToInt(vlIntBytes[0]);
+        if((vlIntBytes.length==1)&&(firstByteValue<=240)){
+            return true;
+        }else if((vlIntBytes.length==3)&&(firstByteValue==241)){
+            return true;
+        }else if((vlIntBytes.length==5)&&(firstByteValue==242)){
+            return true;
+        }else if((vlIntBytes.length==9)&&(firstByteValue==243)){
+            return true;
+        }else {
+            return false;
+        }
+    }
+    public boolean isValidVlIntBytes(){
+        return isValidVlIntBytes(this.VlIntBytes);
+    }
+
+    /**
+     * 判断biginteger是否合法
+     * @param bigInteger
+     * @return
+     */
+    private boolean isValidVlIntValue(BigInteger bigInteger){
+        if(bigInteger.compareTo(BigInteger.valueOf(0))<0){
+            return false;
+        }
+        if(bigInteger.compareTo(BigInteger.valueOf(
+                new Double(pow(2, 64)).longValue())) >= 0){
+            return false;
+        }
         return true;
     }
-
-    //todo:判断biginteger是否合法
-
-    public VlInt(byte[] bytes){
-        this.VlIntBytes=bytes;
-        this.VlIntValue=vlintBytes2bigInteger(bytes);
-        if(this.VlIntValue != null) {
-            this.size = SizeOfVarNumber(this.VlIntValue);
-        }
+    public boolean isValidVlIntValue(){
+        return isValidVlIntValue(this.VlIntValue);
     }
 
+    /**
+     * 判断是否已经初始化
+     * @return
+     */
+    public boolean isInitial(){
+        return this.size>0;
+    }
+
+    /**
+     * 传入的应是一个有效的变长整型数组
+     * @param vlIntBytes
+     */
+    public VlInt(byte[] vlIntBytes){
+        if(!isValidVlIntBytes(vlIntBytes)){
+            throw new Error("VlInt(byte[] bytes): VlIntBytes is invalid.");
+        }
+        this.VlIntBytes=vlIntBytes;
+        this.VlIntValue=vlintBytes2bigInteger(vlIntBytes);
+        this.size = SizeOfVarNumber(this.VlIntValue);
+    }
+
+    /**
+     * 传入的应是一个有效的变长整型value
+     * @param bigInteger
+     */
     public VlInt(BigInteger bigInteger){
+        if(!isValidVlIntValue(bigInteger)){
+            throw new Error("VlInt(BigInteger bigInteger): VlIntValue is invalid.");
+        }
         this.VlIntValue=bigInteger;
         this.VlIntBytes=bigInteger2vlintBytes(bigInteger);
         this.size=SizeOfVarNumber(this.VlIntValue);
     }
 
     public VlInt(SizeT sizeT){
+        if(!sizeT.isInitial()){
+            throw new Error("VlInt(SizeT sizeT): The sizeT is invalid, it should be initial.");
+        }
         this.VlIntBytes=sizeT.getVlIntBytes();
         this.VlIntValue=sizeT.getVlIntValue();
         this.size = sizeT.size();
@@ -90,32 +157,32 @@ public class VlInt {
 
     public VlInt(int i){
         this.VlIntValue=BigInteger.valueOf(i);
+        if(!isValidVlIntValue(this.VlIntValue)){
+            throw new Error("VlInt(int i): The i value is invalid, it is out of the bound.");
+        }
         this.VlIntBytes=bigInteger2vlintBytes(this.VlIntValue);
         this.size=SizeOfVarNumber(this.VlIntValue);
     }
 
     public VlInt(long l){
         this.VlIntValue=BigInteger.valueOf(l);
+        if(!isValidVlIntValue(this.VlIntValue)){
+            throw new Error("VlInt(long l): The l value is invalid, it is out of the bound.");
+        }
         this.VlIntBytes=bigInteger2vlintBytes(this.VlIntValue);
         this.size=SizeOfVarNumber(this.VlIntValue);
     }
 
-    // 传入一个变长无符号字节数组byte[]，将它解析成一个VlInt
-    public VlInt createVlInt(byte[] bytes){
-        return new VlInt(bytes);
-    }
-
-    // 传入一个BigInteger，将它解析成一个VlInt
-    public VlInt createVlIntByBigInteger(BigInteger bigInteger){
-        return new VlInt(bigInteger);
-    }
-
+    /**
+     * 获取bytes
+     * @return
+     */
     public byte[] getVlIntBytes(){
         return this.VlIntBytes;
     }
 
     /**
-     * 将vlint转为一个int输出：需要判断size是不是小于4(1 or 3)
+     * 将vlint转为一个int输出：需要判断size是不是1 or 3
      * @return
      */
     public int getVlIntValue2Int() throws VlIntException {
@@ -126,8 +193,8 @@ public class VlInt {
     }
 
     /**
-     * 将vlint转为一个long输出：需要判断size是不是小于8(5)
-     *
+     * 将vlint转为一个long输出
+     * todo: 理论上存在越界问题
      * @return
      */
     public long getVlIntValue2Long() throws VlIntException {
@@ -188,7 +255,6 @@ public class VlInt {
 
     /**
      * 减去另一个VlInt
-     * todo:暂没考虑两者差值越界int最大值
      * @param vlInt
      * @return
      */
@@ -215,21 +281,24 @@ public class VlInt {
      */
     private byte[] bigInteger2vlintBytes(BigInteger bigInteger){
         byte[] vlintbytes;
-        if(SizeOfVarNumber(bigInteger)==1){
+        int size=SizeOfVarNumber(bigInteger);
+        if(size==1){
             vlintbytes=new byte[1];
             vlintbytes[0]= ByteHelper.uint8ToByte(bigInteger.intValue());
-        }else if(SizeOfVarNumber(bigInteger)==3){
+        }else if(size==3){
             vlintbytes=new byte[3];
             vlintbytes[0]=ByteHelper.uint8ToByte(VlIntExtend2);
             System.arraycopy(ByteHelper.uint16ToByteArray(bigInteger.intValue()),0,vlintbytes,1,2);
-        }else if(SizeOfVarNumber(bigInteger)==5){
+        }else if(size==5){
             vlintbytes=new byte[5];
             vlintbytes[0]=ByteHelper.uint8ToByte(VlIntExtend4);
             System.arraycopy(ByteHelper.uint32ToByteArray(bigInteger.longValue()),0,vlintbytes,1,4);
-        }else{
+        }else if(size==9){
             vlintbytes=new byte[9];
             vlintbytes[0]=ByteHelper.uint8ToByte(VlIntExtend8);
             System.arraycopy(ByteHelper.uint64ToByteArray(bigInteger.longValue()),0,vlintbytes,1,8);
+        }else{
+            throw new Error("VlInt.bigInteger2vlintBytes: VlInt value is invalid, it should be in [0, 2^64).");
         }
         return vlintbytes;
     }
@@ -260,7 +329,7 @@ public class VlInt {
             long value=ByteHelper.uint64ToLong(valueByte);
             vlintValue=BigInteger.valueOf(value);
         }else{
-            return null;
+            throw new Error("VlInt.vlintBytes2bigInteger: VlInt bytes length is invalid, it should be in [1,3,5,9]");
         }
         return vlintValue;
     }
@@ -268,21 +337,11 @@ public class VlInt {
 
     @Override
     public String toString() {
-        return "VlInt{" +
+        return "VlInt{ " +
                 "VlIntBytes=" + Arrays.toString(VlIntBytes) +
                 ", VlIntValue=" + VlIntValue +
                 ", size=" + size +
-                '}';
+                " }";
     }
 
-    // 测试
-    public static void main(String[] args){
-//        BigInteger bigInteger=new BigInteger("3");
-//        VlInt vlInt=new VlInt(bigInteger);
-//        System.out.println(vlInt.isEqual(2));
-            byte[] b1 = new byte[]{(byte) 0xf1,0x00,0x7f};//241,0,127
-            VlInt start1 = new VlInt(b1);
-            System.out.println("VlIntBytes:"+start1.getVlIntBytes().length);
-            System.out.println("VlIntValue:"+start1.getVlIntValue());
-    }
 }
diff --git a/src/main/java/util/ByteHelper.java b/src/main/java/util/ByteHelper.java
index 9590a52..d234b78 100644
--- a/src/main/java/util/ByteHelper.java
+++ b/src/main/java/util/ByteHelper.java
@@ -8,7 +8,7 @@ import java.lang.reflect.Array;
 import java.util.Arrays;
 
 /*
- * @Author: Wang Feng
+ * @Author: Wang Feng、Zhao Feng、Guo Hongyu
  * @Description:常用的数据类型转换。转无符号byte是重点
  * @Version: 1.0.0
  * @Date: 15:40 2021/3/2
diff --git a/src/test/java/encoding/VlIntTest.java b/src/test/java/encoding/VlIntTest.java
index 036133a..0543702 100644
--- a/src/test/java/encoding/VlIntTest.java
+++ b/src/test/java/encoding/VlIntTest.java
@@ -21,6 +21,17 @@ import static org.junit.Assert.*;
 public class VlIntTest {
     private static final org.slf4j.Logger logger = LoggerFactory.getLogger(VlIntTest.class);
 
+    // 测试
+    public static void main(String[] args){
+//        BigInteger bigInteger=new BigInteger("3");
+//        VlInt vlInt=new VlInt(bigInteger);
+//        System.out.println(vlInt.isEqual(2));
+        byte[] b1 = new byte[]{(byte) 0xf1, (byte) 0xff, (byte) 0xff};//241,0,127
+        VlInt start1 = new VlInt(b1);
+        System.out.println("VlIntBytes:"+start1.getVlIntBytes().length);
+        System.out.println("VlIntValue:"+start1.getVlIntValue());
+        System.out.println(start1.toString());
+    }
 
 //    @Test
 //    public void size() {
diff --git a/src/test/java/util/ByteHelperTest.java b/src/test/java/util/ByteHelperTest.java
index ae4c529..c66a537 100644
--- a/src/test/java/util/ByteHelperTest.java
+++ b/src/test/java/util/ByteHelperTest.java
@@ -214,18 +214,21 @@ import static org.junit.Assert.*;
         byte b3 = 0x7f;
         byte b4 = (byte) 0x80;
         byte b5 = (byte) 0xff;
+        byte b6=(byte)0xf1;
         ByteHelper byteHelper = new ByteHelper();
         int a1 = byteHelper.uint8ToInt(b1);
         int a2 = byteHelper.uint8ToInt(b2);
         int a3 = byteHelper.uint8ToInt(b3);
         int a4 = byteHelper.uint8ToInt(b4);
         int a5 = byteHelper.uint8ToInt(b5);
+        int a6=byteHelper.uint8ToInt(b6);
 
         assertEquals(a1,0);
         assertEquals(a2,1);
         assertEquals(a3,127);
         assertEquals(a4,128);
         assertEquals(a5,255);
+        assertEquals(a6,241);
     }
 
     @Test