Stress corrosion cracking(SCC) of reactor components welded 304L stainless steel in deoxygenized solution with different concentration chloride ions was studied using slow strain rate testing (SSRT), the basic water chemistry is simulated in pressure water reactor(PWR) primary loop, high temperature and high pressure water containing boric and lithium ion. Results shown the mechanical properties of welded 304L in 1mg/L chloride solution is equal those of welded 304L in inert nitrogen atmosphere, which implied welded 304L is immune to SCC in deoxygenized solution with low concentration chloride. The tendency of SCC susceptibility of welded 304L increased with increasing chloride ion concentration at range of 1mg/L to 50mg/L. There is not obvious crack on the side of fracture, the lower the chloride concentration, the more obvious the necking-down phenomenon, which implied the fracture mechanics is mainly mechanical fracture. There appeared microcracks source at angular parts, which is relative the stress gathering at these parts. The fracture position all lay in the weld and heat affected zone. There occurred huge deformation in the weld and heat affected zone, the near the fracture, the serious the deformation. The welded parts are weaknesses in the reactor components, which should be key monitoring sites for SCC susceptibility and other properties.