Abstract: During normal operation of nuclear power plant generators, hydrogen gas is charged, and its hydrogen leakage rate is one of the main technical indicators for the operation of steam turbine generator units, as well as an important indicator for the safety evaluation of generators. To prevent serious accidents such as excessive oxygen content or hydrogen leakage caused by leakage, ensure the reliable operation of the generator stator winding, helium leakage detection method was used to detect leakage defects in the stator cooling water system of nuclear power plants. The experimental results showed that the proposed method can accurately determine the location of leakage points, provide support for maintenance work, and can be used for in-service inspection and failure analysis of stator cooling water systems in nuclear power plants.