1Cr11Co3W3NiMoVNbNB imported from Japan for the new high-strength martensitic heat-resistant steel,compared with the traditional 12Cr heat-resistant steel,W,Co elemental content increased to 3%,making the steel has better high-temperature lasting strength,creep resistance,but the weldability is deteriorated. In this paper,research on the weldability of 1Cr11Co3W3NiMoVNbNB heat-resisting steel,and conducts oblique Y-groove and cold-plug test respectively. The results show that the preheating temperature is increased,the welding crack rate of oblique Y-groove is gradually decreased,and the preheated bolt sample is not preheated to be intergranular and transgranular fracture morphology. When the preheating temperature reaches 300 ℃,the fracture is ductile fracture morphology. As the preheat temperature increases,the material’s cold cracking sensitivity decreases.