Abstract: The leakage of 316L austenitic stainless steel caustic storage tank occurred in a nuclear power plant. The cracking causes of the tank were analyzed by macroscopic observation, chemical composition analysis, metallographic testing, hardness testing and residual stress analysis. The results show that the annular cracks parallel to the welding seam and the axial cracks perpendicular to the welding seam were found on the inner wall of the storage tank. The annular cracks were mainly affected by the welding residual tensile stress, while the axial cracks were mainly affected by the cold worked residual tensile stress. These two kinds of cracks were both caustic induced stress corrosion crack.