Abstract: In view of the axial flow fan blade fracture fault occurred in Pingdingshan Power Generation Branch of National Electric Power Investment Group Henan Electric Power Co.，Ltd.，it investigates the monitoring parameters，air flue and leaf before the fault and analyzes the possible causes are as follows：the design flaws，the big gap between the blade-tip region wear plate and cast aluminum blade body，the higher internal stress of wear plate near the blade-tip thinner region，the major casting defects of blade section，etc.