Abstract: In order to reduce the dispersion of incident pluse, the geometric dispersion of incident pulse of conventional split Hopkinson pressure bar（SHPB) were analyzed with dynamic finite element software. It was found that the geometric disperse became intensive along the direction of stress wave propagation, and weakened from center to outside surface. Then, a hollow cone was made coaxially in the end of solid cylindrical impact bar, and the modified bar was called as the hollow cone impact bar. Its effect on the incident pulse dispersion was studied numerically. The results show that the rise-time of incident pulse becomes large, and the geometric dispersion reduces more obviously with the larger cone radius and the smaller cone angle; the frictional effect between the impact bar and incident bar may be negligible, but the phase of oscillation is changed. The effect of modified bar was proved experimentally. The experiment results agree with the theoretical analysis and numerical simulation better.