Airborne laser underwater detecting system is applied in military and civil field. The range gated technology can improve the SNR of laser detecting system efficiently and increase the detecting distance and scope. In this paper, the principle of range gated imaging was expatiated firstly, and then the demands and choice for laser transmitter and receiver were analyzed in detail. The Laser range gated synchronization control system based on TMS320DM642 was designed and the design principle and the practical realization process were implemented. This system can input target distance in real-time and choose the pulse width and delay time easily to gain clear range gated images.