Abstract: A new photoelectric trigger based on rotary mirror was designed. The rotary mirror was composed of a motor and a reflection mirror driven by the motor. The fan-shaped light curtain was formed when the rotary mirror was irradiated by laser. When the light curtain passed throught the object, the photoelectric receiver received the laser reflected twice by the reflecting mirror and produced the trigger signal simultaneously. Then the trigger signal was sampled and digitalized by the collection module. Finally, the signal was transmitted to the controlled device to realize trigger.