Abstract: Ultra-high strength concrete has become an increasingly important material for constructing underground protective structures. However, the lack of reliable material model parameters for C120 ultra-high strength concrete significantly limits the accuracy of numerical simulations for penetration analysis. To address this issue, a comprehensive experimental program was conducted to characterize the static and dynamic mechanical properties of C120 ultra-high strength concrete and calibrate the parameters of the Holmquist-Johnson-Cook (HJC) constitutive model. The experimental program included static uniaxial compression tests, triaxial compression tests, Brazilian splitting tests, quasi-static compression tests under various loading rates, split Hopkinson pressure bar (SHPB) tests, and one-dimensional Lagrangian high-pressure shock tests. Based on the systematic experimental data, the strength parameters, damage parameters, and equation of state parameters of the HJC model were determined through curve fitting methods. The experimental results demonstrated that C120 concrete exhibits significant strain rate sensitivity, with compressive strength increasing substantially as strain rate increases from quasi-static to dynamic loading conditions. The calibrated HJC model parameters include the normalized cohesive strength coefficient, pressure hardening coefficient, and strain rate coefficient. Numerical simulations of projectile penetration into C120 concrete targets were performed using the calibrated parameters in LS-DYNA finite element software. Validation tests were conducted with projectiles penetrating concrete targets at high velocity. The simulation results showed that the residual velocity error was less than three percent compared to experimental measurements, confirming the accuracy of the calibrated model parameters. This research provides reliable material model parameters for anti-penetration performance analysis and numerical simulation of C120 ultra-high strength concrete protective structures.