diff --git a/src/IRIS_Method.c b/src/IRIS_Method.c
index 518f514..929ac6c 100644
--- a/src/IRIS_Method.c
+++ b/src/IRIS_Method.c
@@ -28,7 +28,7 @@ int32_t IRIS_Protocol_Pack(uint8_t Command,uint16_t LenthofIn, uint8_t *BufferIn
     {
         memcpy(&PackData[5],BufferIn,LenthofIn);
     }
-    uint16_t CRC = IRIS_calcCRC(PackData, LenthofIn+5);
+    uint16_t CRC = IRIS_calcCRC(PackData+3, LenthofIn+5);
     PackData[LenthofIn+5] = CRC & 0xFF;
     PackData[LenthofIn+6] = (CRC >> 8) & 0xFF;
     return LenthofIn+7;
@@ -57,7 +57,7 @@ int32_t IRIS_STM32_Protocol_Unpack(uint8_t *PackData, uint16_t LenthofIn, uint8_
     {
         return ERROR_NOT_ENOUGH_DATA;
     }
-    uint16_t CRC = IRIS_calcCRC(PackData, LenthofOut+5);
+    uint16_t CRC = IRIS_calcCRC(PackData+3, LenthofOut+5);
     if(CRC != (PackData[LenthofOut+6] + (PackData[LenthofOut+5] << 8)))
     {
         return ERROR_CRC;
@@ -92,7 +92,7 @@ int32_t IRIS_Protocol_Unpack(uint8_t *PackData, uint16_t LenthofIn, uint8_t Comm
     {
         return ERROR_NOT_ENOUGH_DATA;
     }
-    uint16_t CRC = IRIS_calcCRC(PackData, LenthofOut+5);
+    uint16_t CRC = IRIS_calcCRC(PackData+3, LenthofOut+5);
     if(CRC != (PackData[LenthofOut+6] + (PackData[LenthofOut+5] << 8)))
     {
         return ERROR_CRC;
@@ -154,7 +154,7 @@ int32_t IRIS_Check_Data_Valid(uint8_t *PackData, uint16_t LenthofIn)
     {
         return ERROR_NOT_ENOUGH_DATA;
     }
-    uint16_t CRC = IRIS_calcCRC(PackData, LenthofOut+5);
+    uint16_t CRC = IRIS_calcCRC(PackData+3, LenthofOut+5);
     if(CRC != (PackData[LenthofOut+6] + (PackData[LenthofOut+5] << 8)))
     {
         return ERROR_CRC;