Metallic sandwich plates have been widely used in blast-resistance structures due to the excellent capacity of energy absorption. In this work, dynamic response of square honeycomb sandwich plates is investigated using LS-DYNA. The effect of mass of TNT charge on the deformation and on internal energy of square honeycomb sandwich plate is numerically analyzed. The relationship of deflection, as well as internal energy and the mass of TNT charge is obtained. The performance of square honeycomb sandwich plate is compared with monolithic solid plate with the same mass and blast loading. During the response of sandwich plate, the deformation includes local dent of upper face sheet, overall bending and stretching of both face sheets and buckling of square honeycomb core while the deformation of monolithic solid plate is involved in overall bending and stretching. It denotes that square honeycomb sandwich plate has better capacity of resistance-deformation and energy absorption than that of monolithic solid plate with the same mass and the same blast loading.