Micro-voids significantly affect shock responses of brittle materials. Knowledge about the meso-scale evolution mechanism and macro-scale shock behavior will help to utilize micro-void in applications and avoid its disadvantages. A lattice-spring model, which can represent both elastic property and fracture evolution accurately, is built in this work. Simulations reveal that severe stress relaxation, which is contributed from collapse deformation induced by voids and slippage deformation induced by shear cracks extending from voids, modulates the propagation of shock wave. In a porous brittle material, the shock wave broadens into an elastic wave and a deformation wave. On a macro-scale, the deformation wave behaves as a plastic wave in ductile metal; on a meso-scale, it corresponds to the processes of collapse and slippage deformations. It is found that porosity of the sample determines the Hugoniot elastic limit of material; whereas the porosity and shock stress affect the propagation speed of the deformation wave and stress amplitude in a final state of shock. Brittle materials containing micro-voids have potential applications in complex shock loading experiments, precaution of shock induced function failure, and crashworthiness of buildings. Shock behaviors reported in this work will benefit the design and optimization of shock responses and dynamic mechanical properties of brittle materials used in specific applications.