Abstract: In view of the easy leakage of stainless steel cover in the nuclear power transfer sump, after repeated tests, the helium detection method suitable for the complex structure of stainless steel covering is studied. The leakage of stainless steel covering in Yangjiang nuclear tank is successfully solved, and the similar problems faced by reactor pool, spent fuel pool and fuel transfer pool can also be solved in the future. It provides a reference for the problem of leakage.