In the practical distribution process of quantum key, the transmission loss and efficiency of detectors have a direct impact on the efficiency of key generation. The quantum identity authentication requires both communication sides to ensure the integrity of the authentication information. Considering the problems above, a quantum identity authentication protocol based on photon polarization rotation is proposed, in which repetition coding is used to solve the problem of transmission loss. In order to guarantee the security of protocol, random states are inserted into the adjacencies of the useful authentication quantum states. Security analysis shows that the protocol can successfully resist the intercept-resent attack and beam-splitting attack. Furthermore, a useful authentication system practicable under present technical conditions is designed. It is helpful in applications that transmission loss and detection efficiency are taken into consideration.