Abstract: Range-gated technology, which plays a very important role in the three-dimensional imaging laser radar, is one of simple and effective method to solve the underwater low light level imaging and inhibit backscattering. The principle and application areas of range-gating technology were outlined in this article. Then, according to the demand for real-time imaging, a real-time range-gated imaging system was presented. This system could complete range-gated imaging and solve the target distance just with an imaging picture. By use of the centroid method, the detail of detection range was derived from the imaging system, and the relations between range accuracy and target distance, slice number, signal to noise ratio(SNR) were analyzed. The results of simulation analysis show that the system distance accuracy is greatly influenced by the SNR of the imaging system, and it can achieve better than 0.2 m range accuracy with the SNR greater than 2 000.