Abstract: The creep damage and characteristics of interfacial failure and early failure of welded joints of martensitic heat-resistant steel (9Cr1MoVNbN) and bainitic heat-resistant steel (12Cr2MoWVTiB)with different creep strength of weld have been investigated by means of argon tungsten pulsed arc welding and high temperature accelerated simulation test.And the microstructure was rescarched by scanning electron microscope.The results show that the interfacial creep damage of undermatching welded joint is very serious, and the interfacial failure occurred, and the early failure tendencies are higher than those of overmatching and equalmatching welded joints after accelerated simulating operation 500 h, 1000 h and 1500 h, respectively, on condition that preheat temperature is 250℃, and postweld heat treatment is 750℃×1 h.The creep damage and early failure tendency of overmatching welded joint is higher than that of equalmatching joint, and the creep cavities of weld bainitic heat-resistant seel interface nearly link to form creep cracks.The creep damage and early failure tendency of equalmatching joint are the lowest among the three joints, and few isolated cavities are found in the test.