Abstract: The effects of sulfate and electrode potential on stress corrosion cracking (SCC) behavior of A508/52M dissimilar metal weld in simulated primary water environments of pressurized water reactor (PWR) at 290 ℃ were investigated by means of slow strain rate tensile (SSRT) test and electrode potential control. The results show that the variations of SSRT behaviors with the electrode potential of the weld in the waters without and with sulfate doping were generally similar, that is, ductile failure in the bulk zone of Ni-based weld metal when tested at low potentials, but brittle failure by SCC in the area around the A508/52M interface when tested at high potentials. Doping 10 g·m-3 SO42- into the simulated primary water increased the SCC susceptibility by decreasing the critical potential for SCC. The cracking mechanism and the engineering practical significance were discussed at last.