According to the safety protection problem of the gap between platform edge door and train, the two automatic detection methods of laser correlation and infrared light curtain were introduced, which were wide spread adopted in the industry, and the detection problems of each were pointed out. A foreign object detection scheme based on laser scanning was proposed, including working principle, system design and installation method, etc. The solution was characterized by high reliability and high safety, precise positioning of obstacles, simple installation and unlimited by vehicle gauge, etc., and achieved more reliable safety protection for passengers and driving operations, especially in fully automatic driving mode.