It is an effective method to image and track the distant dark targets by using the laser beam to illuminate them. The SNR of the laser range gated imaging system with range gating and non-range gating are analyzed. It is demonstrated that range gating greatly reduces the lights backscattered by aerosols. The key techniques of the laser range gated imaging system are discussed The advantages and disadvantages of the conventional laser range gated imaging system are analyzed. An improved laser range gated imaging system based on DSP is proposed This system uses the fast DSP controller to accomplish range measurement and range delay and to provide several nanoseconds gated pulse to gate ICCD camera It overcomes some shortcomings of the conventional laser range gated imaging systems, such as need to know preset range delay and laser inner time delay. It can obtain the targets' range information and range-gated image.