Abstract: Currently, both during the construction and operation phases of domestic nuclear power plants, welding repairs for defects in stainless steel water pools are carried out in a dry environment. However, creating a dry environment requires a significant amount of time and manpower, and becomes even more challenging after the nuclear power plant has been in operation for a long time. This article, based on underwater partial dry methods, has developed a set of equipment that can achieve underwater transportation + underwater partial dry welding. Welding repairs for defects on the surface of stainless steel in the spent fuel pool are completed using the plate patch method.This provides a technical foundation for the underwater wall defect repair of spent fuel pools in nuclear power plants.