Abstract: The numerical simulation of explosion in concrete with the hydro-code AUTODYN-2D has been presented. The effects on different method and different mesh size in numerical simulation are studied. With the detail example, the maximum shock pressure of concrete target in radial and axial, overload acceleration of back of target and size of damage section, size of blast pit are computed with Lagrange method and SPH method, which have different mesh size. The simulation results are compared with each other and with experiment results, and the proper simulation method and mesh size are demonstrated to the problem of explosion in concrete medium. Lagrange method is adaptable to simulation the maximum shock pressure of concrete target, especially to the area near the explosive point. SPH method has merit to simulate the shape of blast pit and the throw speed of the break. And 10 mm mesh size to Lagrange method and 3 mm particle size to SPH method are suitable to the example problem.