A lens module detector comprises a platform deck, an image detector and a control module. The platform deck is used for loading the lens module. The image detector is used for moving relative to the platform deck so as to detect the performance of the lens module. The control module is used for controlling the motion of the image detector. The lens module detector also comprises a monitor module and an alarm. The monitor module includes a signal generator and a signal receiver arranged vertically to an optical axis direction of the lens module. The signal generator is used for sending the detecting signals. The signal receiver is used for receiving the detecting signals and judging the lens module to obliquely arrange when the detecting signals are blocked by the lens module. The alarm is connected with the monitor module and used for raising the alarm when the lens module is placed in a slant way. The control module is connected with the monitor module and used for stopping the image detector from moving when the lens module is placed in a slant way so as to stop detecting.