Abstract: Based on mesoscopic damage mechanics, the dynamic numerical code RFPA^2D is developed to simulate the dispersion in wave propagation due to radial inertia effect in large diameter split Hopkinson pressure bar (SHPB), and the influences of waveform such as rectangle stress pulse and triangle stress pulse loaded to incident bar on the dispersion are simulated and analyzed. The results of numerical analysis indicated that the dynamic numerical code RFPA^2D can simulate really the process of stress wave propagation in the pressure bar; when the diameter of SHPB is large, the geometric dispersion effect due to radial inertia become very important; when the appropriate waveform is loaded, the dispersion effect in wave propagation can be reduced, and the triangle wave which may reduce dispersion effect is an appropriate loading waveform in dynamic test of inhomogeneous mediums by using SHPB such as rock and concrete.