Abstract: Feed-water pipe saddle and boiler cylinder after finished welding and stress-relieved heat treatment was found circular crack by detection with drum welding,and expend to internal surface of feed-water pipe saddle and make lengthways crack. Through chemical composition analysis,macroscopic tests,metallographic tests and mechanical property test,the cracking analysis of feed-water pipe saddle was conducted. The result showed that the crack of feed-water pipe saddle was a delayed crack,because welding procedure code didn’t control well,carbon equivalent of welding components have obvious quench trend and welding didn’t avoiding hydrogen treatment,welding structure and larger thickness of welding components occured constrain stress etc.