Abstract: The mechanical properties of frozen soils are significantly affected by temperature and confining pressure. To characterize the effects of temperature, a nonlinear relationship between the three-dimensional tensile strength and the temperature is established, which is incorporated into the yield function based on the coordinate transformation method. To characterize the effects of confining pressure, a potential strength degradation factor is established, which is used to develop the hardening parameters that effectively account for the effects of the confining pressure. Finally, based on the framework of the non-orthogonal elastoplastic model, a non-orthogonal elastoplastic constitutive model for frozen soils that can consider the effects of temperature and confining pressure is developed in the coordinate transformation space. Comparisons between the model predictions and the triaxial compression test results of the frozen silty sand demonstrate that the developed constitutive model can simulate the stress-strain relationship of frozen silty sand under different temperatures and confining pressures. The developed constitutive model characterizes the temperature effects, i.e., the increase in the peak shear strength with decreasing temperature, and the confining pressure effects, i.e., the transition from shear dilation and softening to shear contraction and hardening as reflected by the stress-strain curve under the increasing confining pressure.