A multilayer medium consists of compacted soil, gravel and concrete layers. The damage law of multilayer mediums subjected to blast loading is investigated numerically at various charge weights ranging from 1 to 10kg and burying depths ranging from 0 to 150cm. The numerical results indicate that, in order to increase the energy utilization rate of explosives, charges less than 5kg should be placed in the gravel layer to explode, while those more than 5kg placed in the compacted soil layer. By use of dimensional analysis, the formula for damage effect of multilayer mediums subjected to blast loading is consequently derived. Based on regression analysis of the numerical results, the empirical expressions are established for the effects of charge weights and burying depth on the crater radiuses in the concrete layer, the gravel layer and the compacted soil layer. The expressions can be employed to assess the damage effect of charges blasting in multilayer mediums.