Abstract: The instant disclosure provides a system and method for testing a motion sensor. The motion sensor includes a light-emitting unit and an optical sensing unit. The system includes a detection beam generation module, a control module and a processor module. The detection beam generation module is disposed above the motion sensor for intermittently projecting a detection beam onto the optical sensing unit. The control module is electrically connected to the detection beam generation module for controlling the schedule of the testing light. The processor module is electrically connected to the optical sensing unit for generating a testing result according to the detection beam received by the optical sensing unit.