Abstract: The purpose of the state transition diagram proposed in this paper was to implement the full automatic driving simulation function in the EMU simulation system. The transition diagram was based on the simulation system software of the high-speed EMU developed by the Locomotive & Car Research Institute of China Academy of Railway Sciences Corporation Limited. Based on the configuration parameters of high-speed EMU simulation system and combined with the calculation rules of traction, the automatic driving function of EMU was implemented. In the process of automatic driving, according to the state in the state transition diagram, the program decided the position of the control handle to control the operation of the EMU, and implemented the full-automatic simulation of the driver driving the EMU. Through software simulation, the algorithm is proved practical and reliable. It can ensure that the EMU can drive automatically in the whole journey according to the scheduled acceleration and deceleration mode, stop accurately and prevent over-speed.