Abstract: Steel-tipped 7.62 caliber projectiles had been used to impact the polyurea composite structure with the velocity from 300 mm/s to 450 mm/s. Three types of composite structure composed of LY12 aluminium plate and SPUA-502 polyurea, including uncoated aluminium plate, sandwich structure and coating structure were studied. The effectiveness of the polyurea coating and different structure in terms of reduction of the residual velocity, damage mechanism, kinetic energy absorption of the plates were presented and discussed. In terms of dissipation of kinetic energy of per unit areal density, the coating structure shows the best ability, the pure aluminium plate follows, and the sandwich structure performs the worst. The cross-section microstructure observations indicated that the polyurea coating could limit the expansion of the crater in the rear surface of aluminium plate. Also, a small amount of aluminium scraps are found in PU layers showing that the feasibility of the polyuria coating acting as a protective shield against flying particles and fragments.