Effect of temperature and chloride content on the stress corrosion cracking (SCC) susceptibility of 304 stainless steel welded joints treated by ultrasonic impact treatment (UIT) is investigated in this study. High tensile weld residual stress is an important factor contributing to SCC. UIT can produce compressive stresses on the surface of welded joints that negate the tensile stresses to enhance the SCC resistance of welded joints. In the SCC testing, the specimens were immersed in sodium chloride solution at the temperatures of 200 °C–280 °C in the range of sodium chloride solution from 50 g/L to 200 g/L. During the testing, treated specimens show good SCC resistance with different temperature and consistency of chloride ion. The results show that the SCC susceptibility of 304 stainless steel welded joints reduces with increase of temperature and decrease of chloride ion consistency. The surface roughness of sample after UIT was investigated by portable surface roughness tester. The results reveal that surface of the samples becomes rougher than the original plate with the increase of the impact duration, which contribute to the pitting corrosion of treated specimens. And, the level of pitting corrosion is reduced with increase of temperature.