Abstract: In order to analyze the fracture causes of a turbine blade in a coal-fired power plant and prevent similar accidents from happening again, the blade was examined by macroscopic morphological examination, chemical composition analysis, metallographic examination, scanning eletron microscopy (SEM), energy spectrum analysis, hardness test and normal temperature mechanical property test. According to the latest water quality analysis data of the generating set, the concentrations of S^2- and Cl^- ions in the boiler water were too high. The martensitic stainless steel blade had been working in such corrosive medium for a long time, finally leading to stress corrosion cracking occurring in a small pit where maximum stress concentrated. According to the actual production of the power plant, some measures to prevent the stress corrosion cracking of the blade were put forward from two aspects of corrosive medium and eliminating stress concentration.