In order to optimize the impact hammer structure of high blow energy SC-86H liquid-jet hydraulic hammer, 2 liquid-jet hydraulic hammer with different structures of impact hammer were studied by means of CFD dynamic simulation. The calculation demonstrates that the performance of the newly designed impact hammer has advantages compared with the traditional one under the condition of the same input flow rate; the last impacting velocity is improved, the impact energy and energy utilization increase by 7.9% and 12% in average respectively. The energy consumed by the fluid resistance was reduced by new impact hammer structure to increase the high energy output. In addition, rock breaking efficiency of the hammers was studied based on Ls-dyna nonlinear kinetic analysis and the analysis was carried out on the stress intensity of the newly designed impact hammer. The results show the higher efficiency of energy transfer of impact hammer with new structure, which meets the requirement of fatigue strength checking. At the same last impacting velocity, energy absorption value of rock strata is higher than the traditional impact hammer, while the newly designed impact hammer has high energy absorption ratio. The energy absorption ratios of these two impact hammer models increase nonlinearly as the incident energy increases.