Abstract: The effects of cryogenic treatment and traditional heat treatment on the mechanical properties, dimensional stability and microstructure of 35 CrMo alloy structural steel were studied. The dimensional stability of different processes was evaluated by ring triangle method. The results show that the treatment can increase after quenching and tempering, increasing the cryogenic treatment can increase the tensile strength of 35 CrMo by 32 MPa, the yield strength by 33.5 MPa, the elongation by 26.7%, and the impact toughness remains unchanged. After high temperature tempering, the internal stress of the material is fully released, and the stability of the sample is good. Adding cryogenic treatment can further improve the dimensional stability of the material. The addition of cryogenic treatment after quenching and before tempering can promote the precipitation of carbide particles in 35 CrMo structure.