Based on high temperature compression tests, the flow stress behavior of 20CrMnTiH under the condition of the deformation temperature of 1 123~1 423 K and strain rate of 0.01~10 s-1 was analyzed. The activation energy Q, the stress component n and the material constant α and A were determined by the linear regression method, while Zener-Hollomon parameter was introduced. Then the constitutive model was created according to the creep theory. For model verification, the Z parameter was set as a measurement. The expressions of peak stress and peak strain were then set up with Arrhenius formula, of which the calculated values were brought into the formula based on strain softening exponent. The relationship between stress and strain was derived by nonlinear curve fitting in the whole strain range. The calculated values and the experimental data were in good agreement with a mean error of 6.84%, which verified the accuracy of the Z parameter and the constitutive model.