Bullet penetration test is a classic impact loading test, which involves complex dynamic elastic–plastic response. Conventionally, this process was often described using a single high-strain-rate constitutive model, which could only capture a specific type of failure during the impact damage process. Furthermore, these constitutive models were mostly defined on element and posed the risk of computational divergence(element distortion). In this work, a novel constitutive model for combined tensile–compressive damage in interface element was developed within a Continuous–Discontinuous Element Method(CDEM) framework. This model successfully captures the processes of pit formation and target collapse during projectile penetration. The tension and compression damage parts of the developed interface constitutive model were validated through Brazilian splitting test and interface direct shear test. Subsequently, bullet penetration test is simulated and the post-penetration velocity is compared with published results from other studies, with computational errors found to be within 2.56%, thus validating the accuracy of the developed interface constitutive model.