Abstract: The fracture of 12%Cr bolt of high-conductor flange of No.3 steam turbine in a power plant was analyzed by macroscopic inspection, chemical composition analysis, mechanical property test, microstructure analysis, fracture morphology and energy spectrum analysis. The results show that the fracture mechanism of 13^# fracture bolt is dominated by creep brittle fracture, and the corrosion accelerates the crack failure process. According to the analysis of the fracture causes of high temperature bolt, the relevant opinions on strengthening the supervision of high temperature fastening bolts in various parts of steam turbines are proposed.