Abstract: The cracks were found in border of centrifugal wheel blade of an engine.The reason of cracks wasanalyzed by means of physical testing and chemical analysis,quantitative analysis and calculations for crackpropagation life and expand total percentage of the propagation life.The results showed that the cracks in blade washigh cycle and low cycle composite fatigue cracks,and fatigue cracking occured in blade by large stress of abnormalvibration.