Abstract: In order to study the physical mechanism of explosion field in concrete, a code MMIC-3D is proposed based on the 3D Youngs interface reconstruction algorithm. The formation and development process of the cavity and the law of bulge motion during the explosion in semi-infinite concrete are simulated. The three-dimensional numerical results of the explosion field in the semi-infinite concrete medium are obtained. The results showed that the computational data agree with the experimental phenomena and the physical law, which indicates that the algorithm and the hydrocode presented in this paper are correct, and can provide instruction for engineering designs.