diff --git a/src/main/java/com/sunyard/sge/database/SydApiSM4.java b/src/main/java/com/sunyard/sge/database/SydApiSM4.java
index 893f60d..20a453c 100644
--- a/src/main/java/com/sunyard/sge/database/SydApiSM4.java
+++ b/src/main/java/com/sunyard/sge/database/SydApiSM4.java
@@ -98,7 +98,7 @@ public class SydApiSM4 {
         }
         else {
             if (0 == sourceWrap.array().length) {
-                if (plength<16){
+                if (plength<16||plength/16<2){
                     api.SYD_SM4_LongData(iKeyIndex, new byte[0], iPkgNum, iFlag);
                     ByteBuffer bufferResult = ByteBuffer.allocate(sourceWrap.array().length + plength);
                     bufferResult.put(sourceWrap);
@@ -125,7 +125,7 @@ public class SydApiSM4 {
                 return api.SYD_SM4_LongData(iKeyIndex, pcdataResult, iPkgNum, iFlag);
 
             } else {
-                if (16 > pcData.length + sourceWrap.array().length) {
+                if (16 > pcData.length + sourceWrap.array().length||(pcData.length + sourceWrap.array().length)/16<2) {
                     ByteBuffer bufferResult = ByteBuffer.allocate(sourceWrap.array().length + plength);
                     bufferResult.put(sourceWrap.array());
                     bufferResult.put(pcData);