With the rapid development of high-speed railway, the research of the data secure transmission of high-speed railway based on cloud computing and real-time online analysis have become the hot topics. Aiming at the problem of the data secure authentication in the process of the data transmission at high-speed rail, a data secure transmission protocol for high-speed rail sensor system based on SM2 signature algorithm is designed. The traffic state data collected by the sensor network are transmitted to the cloud service platform by the security protocol based on SM2 signature algorithm, and the secure interaction between the high-speed rail traveling data recorder and the cloud service platform is realized. Therefore, the reliability and integrity of data transmission are improved. Finally, the experiment and simulation of secure transmission protocol are carried out, and the result shows that the protocol has high efficiency and security in the process of high-speed railway data transmission.