Range gated laser active imaging can overcome the disadvantage of passive imaging and get clear imaging target under weak light conditions. According to the basic processes of imaging,seven mathematical models of laser imaging chain were established,including laser emission model,target model,the target and platform motion model,atmospheric model,receiving optics model,ICCD imaging model and noise model. The transfer of laser energy through each link is studied,laser image under atmospheric conditions is simulated. Through analysis of the experimental images,the correctness of the model is verified.