TC4 titanium alloy material will generate significant spring back during the bending process, and its elastic modulus has a significant impact on spring back. However, previous studies have not considered the change in elastic modulus during the plastic strain change process of the material. This study focuses on TC4 titanium alloy and conducts uniaxial tensile and cyclic loading unloading experiments to determine the anisotropy parameters and the variation of material elastic modulus with plastic strain. On this basis, a mathematical model for the variable elastic modulus of TC4 titanium alloy was established. Based on three different constitutive models, namely YLD2000-2D yield criterion and variable elastic modulus, YLD2000-2D anisotropy, and Mises isotropy, numerical simulations were conducted on the five point bending process of TC4 titanium alloy plates at room temperature. In order to verify the numerical simulation results, a five point bending experiment was conducted on TC4 sheets at room temperature. The results showed that the anisotropic constitutive model and the mathematical model of variable elastic modulus significantly improved the prediction accuracy of TC4 titanium alloy bending spring back, the highest prediction accuracy increased by 31.18%.