Abstract: Based on experimental results, adopting damage and failure principle of Ottosen, this paper proposes a dynamic constitutive model to describe mechanical behavior of concrete subjected to impact loading. Macroscopically, concrete is assumed to be homogeneous and consecutive, but a large amount of micro-crack defects are distributed randomly throughout the concrete. Assuming these micro-cracks satisfy perfect micro-crack system conditions, the volume ratio of micro-cracks in the sample is used to describe the decrease in macro-mechanical properties of concrete. And the development of damage is presented. A comparison between model prediction and experiment results shows that the model prediction agrees well with experiment results. So it can be used to simulate the dynamic behavior of concrete under impact loading.