Abstract: The blade of forced draft fan of a thermal power plant in Qinghai province fractured during operation.The fracture reason of the blade was analyzed by means of mechanical property test, micro morphology, energy spectrum analysis, metallographic observation and combined with the blade working condition.The results show that the fracture mode of the blade is stress corrosion cracking.The blade surface corrosion is serious, and the corrosion pit appears.During high - speed operation, the blade receives wind and centrifugal force, and it produces stress concentration at corrosion pit, causes initiation and expansion of cracks, and eventually causes the instability and fracture of the blade.