Abstract: The electric pulse discharge experimental platform of 20 kV/40 kJ was set up and the impact fracture test of large cement sample was carried out. In order to simulate the actual working conditions, the discharge electrode was put into an insulated sleeve with perforation. While discharging in water, the directional impact pressure wave was produced in the rock sample, and the shock wave acted on the rock layer to produce cracks. The experimental results show that when the shock wave produced by the repeated electric pulse discharge acted on the big cement sample, it caused cracks on a certain scale, and the cracks on the rock sample surface are symmetrical. There was a certain energy loss when the shock wave moved through the insulating sleeve and part of the shock wave pressure was applied to the insulating sleeve, but the insulating sleeve did not deform during the discharging. The damage of electric pulse discharge on insulating sleeve is minimal.