In order to improve the availability of EMUs in the event of a grounding fault in the traction system, and reduce the difficulty of troubleshooting for after-sales personnel, a method for automatically locating the ground point was proposed, this method combined voltage type grounding dection circuit and current type grounding dection circuit, which could realize the function of automatically locating the ground point and automatically removing the grounding part through software. The verification showed that the method in this paper could automatically locate the grounding positions, and automatically perform different levels of protection according to different grounding positions through software, which improved the availability of the train and greatly improved the efficiency of dealing with grounding fault, and provided a reference for the design of subsequent EMUs.