Aiming at shortage of method existed in subway platform screen door（PSD）detects the minimum size of obstacles is 4 mm×40 mm when using the method of door speed curve changes a method to detect obstacles using infrared light screen is proposed

combined with DSP control technology of brushless DC motor（BLDCM）and fuzzy PID control algorithm to realize obstacle detection of subway platform screen door.Mathematical model of the whole system is constructed and simulation in Matlab/Simulink.The simulation results show that the subway platform screen door obstacles detecting system based on infrared screen can solve the shortage which existed in the existing subway platform screen door obstacles detecting system.