Abstract: The damage constitutive model proposed by Krajcinovic and Lemaitre was improved according to the result of the strain fatigue tests of Ti-6Al-4V titanium alloy based on the continuum damage mechanics (CMD), then parameters of the damage model were determined through fitting the strain fatigue data. The damage model was compiled into USDFLD subroutine, then this USDFLD subroutine was coupled into ABAQUS software. The combined hardening model mixed with Chaboche nonlinear kinematic hardening and nonlinear isotropic hardening was used to describe the elastic and plastic behavior, the parameters of the combined hardening model were determined through fitting the strain fatigue data. The fatigue damage evolutions of the material under different strain amplitude were simulated. The experiment results showed that the prediction life based on the damage model was in good agreement with the experimental life. Comparing the results of experiments and simulations, the average error was 3.878%.