Abstract: The mechanical properties of frozen soil are significantly affected by temperature and confining pressure. To characterize the effect of temperature, a nonlinear relationship between the three-dimensional tensile strength and temperature is established in this paper, which is incorporated into the yield function based on the coordinate transformation method. To characterize the effect of confining pressure, a potential strength degradation factor is established in this paper, which is used to develop the hardening parameters that effectively account for the effect of the confining pressure. Finally, based on the framework of the non-orthogonal elastoplastic model, a non-orthogonal elastoplastic constitutive model for frozen soil 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 pressure. The developed constitutive model not only characterizes the temperature effect, i.e., the increase in peak shear strength with decreasing temperature, but also the confining pressure effect, i.e., the transition from shear dilation and softening to shear contraction and hardening as reflected by the stress-strain curve under conditions of increasing confining pressure.