Abstract: Through analysis of cracking causes in boiler canister of SUS304 (0Cr18Ni9) austenitic stainless steels,the reason for its inactivation was pointed out. After self-coiling welding boiler canister and cover were welded,at the self-coiling stress of boiler canister and welding stress of boiler canister and cover,the self-coiling welding boiler canister appeared stress corrosion cracking at the pitting corrosion by chloride inducement and sulfide accelerating.