Abstract: Impact experiments of man-made rock with different porosities were carried out with Split Hopkinson Pressure Bar (SHPB). The characteristic of energy dissipation and the influence of rock porosity on energy dissipation were investigated during the impact process. Meanwhile, the relation between the energy dissipation of critical failure and rock porosity was also analyzed. The experimental results indicate that the porosity of rock plays an important role in the energy dissipation process. The energy dissipation increases as the porosity of man-made rock increases at the same impact velocity, and it decreases as the rock porosity increases under the critical damage of man-made rock. The energy dissipation is related to the internal damage of rock to some extent.