By improving the traditional digital concrete modeling method, the new defective concrete model was established. Three cases were simulated based on this model. The influence of initial defectiveness on the dynamic strength was investigated. The result shows that: 1) At initial stage, the influence of the initial defectiveness on the dynamic strength becomes more obviously with the increasing of the loading speed; 2) Regardless of the same loading speed, the influence becomes less obviously when the load reaches the strength point of the concrete; 3)The simulation result is compared with the test result, and it is deduced that the new model has higher computational accuracy and the result is more rational, and it can take the place of the traditional digital concrete model in practice.