Aiming at the mispunchproblem of emulsion impact hammer, the cone-type piston buffering structure was adopted to minimize the impact.Impact process simulation model of differential connection piston was built usingAMESim software, the influences of different buffer length, conical angles and buffer clearance on the terminal velocity and pressure were analyzed according to the model and optimum parameters (half cone angle 5 degrees, length 50mm as well as clearance0.25mm) were determined. The collision progress between piston and the guide sleeve at 2m/ssimulated by LS-DYNA software shows that the maximum stress is 674MPa which locates at at the edge of the liquid inlet hole of guide sleeve, and the maximum stress on interface is less than 400MPa, both of them area lower than theyield strength of materials, so the guide sleeve is of shock resistance. However, it is found to have rebounding phenomenon during the buffering process and the mispunch should be attentively prevented.