Abstract: The reason of cracking of 304L stainless steel covered on the refueling pool was found out through the analyses of macrostructure, microstructure, chemical composition, mechanical properties, morphology of fracture and chemical composition of corrosion products. The results show that it was typical stress corrosion cracking of 304L stainless steel induced by Cl-.The main source of Cl-is the Cl emulsion copolymerization used in the course of the execution of concrete. It was suggested that clear the concrete with Cl emulsion copolymerization thoroughly during subsequent maintenance of the stainless steel panel, reinforce the water quality control and concrete addition management during similar concrete executions.