Accidental explosions and terrorist bomb attacks threat lives worldwide. To protect vehicles and civil infrastructure from close-in, a novel sandwich panel with re-entrant hexagon honeycomb core was proposed. Physical tests and numerical simulations of the proposed sandwich panel have been carried out in the previous studies. The re-entrant honeycomb showed obvious auxetic characteristics under the blast loading with much improved energy absorption capability. Based on this finding, a new protect system is proposed in this research. The structure consists of the sandwich panel studied previously and a steel plate with the same planar size covering the sandwich panel, i.e. steel cover. To further reveal the blast-resistant performance of the proposed protect system, parametric study with respect to the boundary conditions and the blast load intensity were thoroughly carried out. Firstly, the configuration of the protect system is introduced, the finite element model of the protect system is then presented and validated. Secondly, results of the parametric studies are presented. The structure's parameters MaxD (maximum back face deflection) and ASEA (areal specific energy absorption) are chosen as the indicators to evaluate the blast resistance of the protect system. It was found that boundary conditions show obvious effect on MaxD. However, the boundary conditions showed little effect on ASEA. Specifically, the boundary conditions did not affect the energy absorption capability of the protect system, they only changed the distribution of the internal energy among different parts of the protect system. Finally, multi-objective optimization of the proposed protect system was conducted and the Pareto front for multiple blast-resistant objectives was achieved and discussed. The results of the current study provide new information for real engineering applications of such protect systems for blast protection.