High-repetition-rate range-gated underwater lidar imaging is achieved by multi-pulse accumulation.Noise characteristic analysis of the high-repetition-rate range-gated underwater lidar image is a necessary step for further improving the imaging quality by image post-processing.Through an analysis of the characteristics of both additive noise and multiplicative noise,noise characteristics of the single pulse range-gated underwater lidar image,high-repetition-rate range-gated underwater lidar image and multi-frame averaged high-repetition-rate range-gated underwater lidar image are analyzed.The experimental results show that: 1) The single pulse range-gated underwater lidar image is mainly affected by the multiplicative noise; 2) The high-repetition-rate range-gated underwater lidar image is affected by both the additive noise and multiplicative noise; and 3) After multi-frame averaged,the high-repetition-rate range-gated underwater lidar image mainly contains multiplicative noises.