Abstract: In order to solve the problem of finding the sniper quickly in security, a system using the cat-eye effect principle of sniper scope to find a target is designed. The system is different from that of traditional design of lighting source. It is a system based on semiconductor modulated laser, which replaces CW laser source, and works with modulated signal to scan the field. A CCD is used to capture the active and passive echo image. According to the target echoes image at different distance, the algorithm can be implemented in embedded DSP high-speed processing platform for the near and far targets respectively. The results, obtained in the field experimental, showed that the new system increases the detection rate, and reduces the incidence of false alarms. The system accurately detected the target of 300m and 800m in distance with a real-time processing speed of 10 fps.