In order to describe the stress-strain relationship of 35CrMo steel and establish constitutive model of material, the high temperature thermal simulation compression experiment of hot rolled 35CrMo steel is conducted by the Gleeble3800 thermal simulation machine, the effect ofdeformation temperature and strain rate on the material flow stress of 35CrMo steel is studied under the condition that the deformation temperature is 800， 900,1 000,1 100,1 200 ℃ and the strain rate are 0.01,0.1,1,10 s^-1. The experimental results show that there are two stress-strain relationships, dynamic recovery and dynamic recrystallization, in the high-temperature deformation of 35CrMo steel.The constitutive equation of 35CrMo steel peak stress is established indirectly by calculating the relationship between critical strain and peak strain, and the accuracy of the constitutive equation is verified.This constitutive equation can well describe the stress-strain relationship under the thermal deformation condition of 35CrMo steel, and ithas basic theoretical significance for guidingthe thermal formingprocess design and numerical simulation of 35CrMo steel.