Abstract: The thesis reviewed the development of the Automatic Train Operation(ATO) System and designed the train speed closed-loop simulation model, in which the PID Algorithm was used, when the V-S curve was input to the System in the PID controller, the output was satisfactory followed the start-up phase of the train. During the intermediate speed fluctuation stage, there would be a spike wave phenomena in the output of the acceleration curve. Problems of ATO System based on PID Algorithm was analyzed.