Abstract: The galvanic corrosion behavior of 25Cr2Ni2MoV overlaying welded nuclear steam turbine rotor was investigated by macro-electrochemical tests and immersion tests in chloride solution at 80 ℃. The results of electrochemical experiments show that the weld metal is the weak corrosion zone, and the corrosion potential from low to high is the heat-affected zone, the base metal, and the weld metal. The results of the immersion tests show that as the area of the BM increases, the average corrosion thickness of the WM gradually increases Furthermore, the galvanic corrosion finite element model of welded joint was established by using the electrochemical parameters obtained from macro electrochemical test. The results show that the finite element simulation results can effectively simulate the galvanic corrosion behavior of overlaying welding joint and provide galvanic corrosion rate prediction for actual production.