This paper proposes one kind of MD5-based error-detecting mechanism. The 128-bit MD5 code is compressed into 16-bit error-detecting code in order to substitute for that computed with CRC or checksum. In this mechanism, computer-simulating technology is used to simulate natural and manual attacks. The evaluation method is to corrupt the data of each packet which is produced by a random number generator and to record the detecting result for the same data with its corrupted copy. The results show that these three error-detecting codes have the strong ability against natural attacks, but for manual attacks, CRC and checksum have no ability and MD5-based error-detecting mechanism has the strong detecting ability. At the same time, the 128bit-to-16bit compression for MD5 has less impact on its error-detecting ability.