Seal weld repairing method and system of nuclear power plant

The invention discloses a seal weld repairing method and a system of a nuclear power plant, and solves the technical problems of complex welding line defect repairing process and high welding risk of the nuclear power plant seal weld in the prior art. The method comprises the following steps: (1) multiple first holes are drilled in a welding line defect central line; (2) hole bridges among the first holes are broken to form a groove; (3) a second hole is drilled in a welding line far from the groove by a preset distance for charging argon into a back surface cavity of a welding operation panel; (4) the back surface cavity is cleaned; and the repairing weld is performed for the groove and the second hole; and (5) the appearance, liquid permeation and water pressure test inspections are performed for a repairing welding line. The method realizes the technical effects of easy repairing weld process, provision of sufficient inert gas protection, removal of residual moisture and guarantee of welding quality.