Abstract: In order to effectively evaluate and improve the security of the transmission protocol of the railway signal system, this article analyzed the timeliness of the safety algorithm in the railway signal system.Through the simulation experiment, the article evaluated four hash functions and six encryption and decryption functions quantitatively.The experimental results show that the processing time of the security algorithm increases with the length of the application data; the working mode of the encryption and decryption function has little effect on the timeliness; the decryption algorithm of the encryption and decryption function consumes more time than the encryption algorithm; the SHA256 hash function is the preferred scheme to ensure the data integrity security algorithm; the Twofish algorithm is the preferred scheme of the encryption and decryption algorithm.This conclusion provides a reference for the selection of safety algorithm of railway signal system.