The modified theory of elastic stress waves states that the wave equations on volume strain are consistent with existing theories, but a set of weakly coupled wave equations on volume strain and partial strain has been developed. Aiming at the fluctuation problem of stress wave under the impact of concentrated load on rectangular plate, two sets of control equations for stress wave propagation and the fluctuation boundary conditions of loading surface and free surface are established. The finite difference method is used to solve the wave equation, and the stress wave is simulated numerically for the propagation of the main and secondary waves and the reflection process of oblique incident waves on the free plane. The partial strain splits into two parts during propagation, one part propagates together with the volume strain to form the main wave, and the other part propagates slower to form a secondary wave. The numerical simulation results show that the propagation image of the stress waves in the nanocalcium glass plate under shock load is completely consistent.