Abstract: High residual stress introduced at the welding joint can affect the stress corrosion cracking (SCC) property remarkably. The SCC growth rates of specimens prepared from a 316LN stainless steel AP1000 primary pipe welding mockup were measured in high temperature and high pressure water. The results obtained from heat affected zone (HAZ) of the specimens show that the welding residual stress has significant effects on accelerating crack growth rate, and the stress-relieved specimen has lower crack growth rate than the after-welding specimen. The acceleration of crack growth rate by residual stress seems to be greater in normal hydrogenated PWR water chemistry.