Abstract: Based on the principle of phase laser ranging, the idea of using phase laser range finder for underwater ranging was proposed, and the feasibility of underwater phase laser ranging was analyzed in principle. Through the underwater distance measurement experiments, the feasibility of underwater phase laser ranging was verified, the range calibration algorithm for underwater phase laser range finder was completed, and the effects of water turbidity on the dynamic range and distance measurement accuracy of laser ranging were explored. The experimental results show that the average ranging error of underwater laser range finder after calibration is not more than 3 mm in the range of 3.5 m, and there is an exponential decay relationship between range and water turbidity. The underwater phase laser range finder provides a new method for the detection of underwater distance, which can achieve accurate ranging at short range of underwater target.