Abstract: A systematical analysis on chemical compositions,mechanical properties,corrosion products and fracture surface morphology of failure Inconel 625 bellows by means of various techniques including chemical analysis,TEM,XPS and SEM.The results showed that the failure of the bellows is attributed to the corrosion fatigue.High temperature oxidation-sulfidation corrosion in the corrosive environment,brings about initial cracks on the surface where is under high stress and fatigue cracks develop into fatigue fracture under alternative stress.To reduce the corrosion and stress can avoid or moderate the corrosion fatigue and prolong the lifetime of the bellows service.