As a safe,clean and efficient energy source,the development of nuclear power will be the main trend of power development in the future. Key components and reactor internals of nuclear power plants need to be repaired and decommissioned after long-term operation in a high-radiation and high-temperature environment. To reduce the hazards of nuclear radiation on the operator,repair work needs to be carried out underwater. Underwater laser processing technology has broad application prospects in the field of nuclear power due to the characteristics of low heat input,precise acting position,and long-distance transmission. In this article,it summarized the principle and research status of underwater laser processing technology,such as underwater laser welding,peening,cutting,mainly introduced the application of underwater laser processing technology in nuclear power plant maintenance,it also pointed out the future development trend and key research directions of underwater laser processing technology.