Warm frozen soil is very sensitive to temperature change in the near phase transition region, and the relationship between temperature and physical and mechanical properties can be expressed by constitutive model. Based on the strain equivalent theory of damage mechanics, the damage model of warm frozen soil structure under the coupling action of stress and temperature is established. Based on Mohr- Coulomb criterion, the nominal stress is used to represent the stress damage of frozen soil element, the initial elastic modulus is used to represent the temperature damage, and the composite damage factor is introduced to describe the coupling relationship between them. Two methods are used to obtain the shape parameters and scale parameters of the coupled damage model: method 1 is the full fitting method based on the experimental data; method 2 is the semi theoretical semi fitting method based on the characteristic points of the stress-strain curve. Through the triaxial compression test of frozen sand, it is proved that the simulation results of the stress-temperature coupled damage model are in good agreement with the experimental curves. Based on the experimental results, the results of the two methods are compared, and it is proved that method 2 is better than method 1 under the condition of strain softening. By comparing the predicted results of stress temperature coupled damage model and single stress damage model, it is shown that the former can effectively reduce the influence of parameter estimation error on the results and improve the stability of the model.