For addressing the two focus issues under research , security authentication protocol and the multi-tag anti-collision algorithm in the field of Radio Frequency IDentification (RFID), a Code Division Multiple Access (CDMA)-based anti-collision algorithm of the RFID authentication protocol is presented in this paper. The authentication protocol supports dynamic updates of the key and resists database synchronization attacks by using flag mechanism to select spare key. Meanwhile, by combining with CDMA and by retransmitting random number to select spreading code, the authentication protocol solves recognition of tags due to data collisions during the multi-tag identification by one-time retransmission. Firstly, the process of the authentication protocol and an anti-collision theory is described. Secondly, the SVO logic is used to prove correctness of the protocol in theory. Finally, numerical analysis of the system throughput applying the protocol shows that its throughput efficiency is higher than the traditional one.