The invention provides a rapid identity authentication method based on a C/S mode. The rapid identity authentication method based on the C/S mode comprises the steps that (1) a client and a server generate respective random numbers in sequence, carry out encryption on the random numbers, send the encrypted random numbers to each other, carry out another encryption on decrypted random number data of the opposite side, and send the encrypted random number data back to each other, and in the process, the server carries out legitimacy authentication on identity information of the client, and encryption processing is carried out after the client passes through the authentication; (2) the client and the server carry out decryption on the returned data to obtain the random numbers which are processed through encryption protection transmission, comparison is carried out between the random numbers and the random numbers generated by the client, comparison is carried out between the random numbers and the random numbers generated by the server, and the client and the server pass through bidirectional identity authentication when the random numbers and the random numbers generated by the client and the server are consistent. According to the rapid identity authentication method based on the C/S mode, the legitimacy authentication processing process of the client to certificates of the server in the process of authentication is omitted, the process is simple, the process of authentication is rapidly optimized, safety can be ensured, and the rapid identity authentication method based on the C/S mode is especially applicable to the identity authentication processing process of a mobile terminal when the mobile terminal which is limited in terminal operation resource and network transmission capacity is connected to an application system.