This paper describes the creep rupture behaviour, hardness distribution and microstructure of weldment made by submerge arc welding for W strengthened P92 steel. The cross-weld creep tests were carried out at 923K and at stress ranging from 100 to 130MPa. For stress below 120MPa, weld-joints ruptured by the type IV crack, which located in their fine-grained heat-affected zone (FGHAZ) with the smallest measured cross-weld hardness. A strong drop in creep rupture strength of weldment was induced by brittle type IV failure. In addition to coarsening of M 23 C 6 carbides and an equiaxed fine grains in FGHAZ, intermetallic Fe 2 (Mo,W) Laves phase precipitated on grain boundaries during creep is probably the significant factors caused the type IV failure.