Abstract: In order to study microscopic failure mechanism of concrete under impact loading,the concrete is considered as a three-phase composite composed of matrix,aggregate and interface between them.The number of aggregates is calculated by using Walraven J.C formula and meso-scale structure is represented with random aggregate model by using Monte-Carlo method.The bilinear damage evolution model is adopted to describe the meso-element's damage devolution.The microscopic failure mechanism of concrete under impact loading is simulated with nonlinear finite element method,stress-strain curve of specimen and its dynamic compressive strength are got.The results show that the numerical solutions are fitted with experiment results.