In the existing RFID system, the shared key which is used in the authentication between tag and reader is set in advance, but there are some security flaws in the system. In order to solve the security problem, this paper proposes a new key wireless dynamic generation algorithm based on Syn. The algorithm uses the random number generated by the tag and the reader to generate the shared key dynamically through the Syn operation to ensure the security of the shared key. Through the security analysis, it can be found that the algorithm can effectively resist the attacks such as impersonation attack and brute force attack