Abstract: The P92 welded joint stress-rupture test in tension was performed at 600℃/10 000 h,Extrapolation the stress-rupture of P92 welded joint after 100 000 h under 600℃ was 116 MPa.The microstructure of P92 welded joints before and after the test were studied using metallographic microscope,TEM and EDS.The results showed that the microstructure of the welded joint was martensitem,the major precipitation M₂₃C₆ and high-density dislocation in transgranular.The microstructure of P92 weld joint was still lath martensite after 9395.8h stress-rupture test,The original lath was still clear,high density dislocation still exist,the new phase precipitates increase in intragranular.Furthermore,it was found that the high rupture strength of P92 weld joint was mainly due to the precipitation of M₂₃C₆,lath martensite and high density dislocation.