The susceptibility of 10CrMo910 steel to cooling cracking and stress relief cracking have been investigated by deep notch implant test.The properties of 10CrMo910 steel thick wall pipe joints with and without PWHT have been compared by high temperature test.The results show:1) 10CrMo910 steel pipe joint with thickness 35mm can be prevented from cooling cracking by a 180-200℃ preheating;2)10CrMO910 steel is very lightly sensible to stress relief cracking.Stress relief cracking will not occur in 10CrMo910 steel pipe joints without PWHT during high temperature service.3) Pipe joint without PWHT has higher mechanical properlies.Actually the PWHT is a superhigh temperature operation process reducing hot strength of joints.4) It is feasible to cancel the PWHT of 10CrMo910 steel joints with ≤273mm

δ≤35mm.