Abstract: The synchronous optical pen electronic whiteboard system in the present invention introduces an image sensor with a global shutter, optical pen pulsing light-emission and synchronizing signal transmitter and receiver. The light pulsing of the optical pen and the exposure of the image sensor coincide by synchronizing signal so as to realize the object of increasing signal-to-noise-ratio. A synchronizing signal sender can be arranged in the optical pen and a synchronizing signal receiver arranged in a signal receiving device, or a synchronizing signal sender can be arranged in the signal receiving device and a synchronizing signal receiver arranged in the optical pen. The coincidence of light pulsing and the exposure can be realized in the two solutions, thereby realizing the object of the present invention. By using the solution of the present invention, the power consumption of the optical pen can be reduced effectively and the signal to noise ratio of the system can be effectively increased in the meanwhile.