The utility model provides a detect device of plane drawback, a serial communication port, the device include darkroom (1), camera (2), light source (3), second pointolite (4), third pointolite (5) and the plane rack (four to six -tenehs) that awaits measuring in the first place to install on the first side in darkroom camera (2), and install respectively so that its place plane and first side are parallel, and be located outside the lens coverage of camera (2) light source (3), second pointolite (4) and third pointolite (5) in the first place. In the method and system for, through shooing under three pointolite condition to handle data, realized plane surface defect's high precision measurement.