Aimed at the invalid stop of the elevator, this project used the self-designed Lift car device to test the elevator operational aspects of many typical environments, such as hospital, school, business building. The result showed that invalid start took an average rate at 25%, among which most were invalid stop, energy consumption was serious. Considering the similarity of “no response to the request outside the lift car after the car is full”, this device virtualized the full load condition of the lift car timely and accurately after testing the waiting passengers outside the cabin, so that the invalid stop is prevented, and it saved energy evidently.