haha，问题已经解决了。

Private Sub MSComm1_OnComm()

Dim DealStrBack() As Byte '新增变量

Select Case MSComm1.CommEvent
Case comEvReceive, 判断为接收事件
MSComm1.InputLen = CmdLenth '接收数据的长度
Select Case CommFlag
Case 1

DealStrBack = MSComm1.Input
CommDealFlag = 1


Case 2
ReadStrBack = MSComm1.Input '接收数据
CommDealFlag = 2
End Select
MSComm1.InBufferCount = 0
CommFlag = 0
Beep
End Select
Timer2.Enabled = True
RunStrBack = DealStrBack ’新增数据转存语句

End Sub

我也不懂什么原因，加了前面有注释的语句就可以了。