Abstract: The maximum principal stress and Von Mises equivalent stress were simulated by FEM under the condition of 560℃ and applied stress lever is 100 MPa, 120 MPa, 140 MPa, respectively.The simulation results were validated with invariable stress accelerating test.The results show that the maximum principal stress is quit high in the vicinity of weld/12Cr1MoV interface for undermatching weld joint, and creep cavities are easy to form in the weld/12Cr1MoV interface.With the increase of the acting stress, the maximum principal stress in the vicinity of weld/12Cr1MoV interface is increasing rapidly.However, the Von Mises equivalent stress is relatively low, and creep cavities are difficult of expansion.And only isolated cavities were found after accelerating test, early failure tendency is low.The stress concentrations of weld/12Cr1MoV interface is serious, the Von Mises equivalent stress is relatively high in the vicinity of weld/12Cr1MoV interface for overmatching weld joint, creep cavities are easy to form and expand.The creep damage and early failure tendency of overmatching weld joint are higher than those of undermatching weld joint, and the interfacial creep rupture occurred after the accelerating test.Therefore, using undermatching joint is reasonable for the dissimilar welded joint between martensitic and pearlitic steel.