Abstract: With 9Cr-2W-3Co martensitic heat resistant steel as the research object, the high temperature creep endurance testing machine was used for stress rupture test at 625 ℃ and under different stresses (100, 110, 120, 130, 140, 150 MPa). The microstructure, precipitated phase characteristics and the stress-rupture limit of the test steel after creep fracture were studied. The results show that compared with the original structure, after creep fracture at 100 MPa, the martensitic slats in the matrix of test steel basically disappeared, the dislocation density decreased, the precipitated phase coarsed, and coarse Laves phase Fe₂(W, Mo) precipitated around Cr₂₃C₆ distributed along the original austenite grain boundary. The effect of solution strengthening, precipitation strengthening and dislocation strengthening of test steel was weakened. By fitting the relationship between the different loading stresses and the long breaking time, it was deduced that the stress-rupture limit of test steel at 625 ℃ was 93 MPa.