The purpose of this study is to explore a new type of structure design and injecting material selection of the composite sandwich bulletproof system. A reentrant hexagonal honeycomb with the negative Poisson's ratio effect was designed. Thermoplastic polyurethanes (TPU), polypropylene (PP) and polycarbonate (PC) were chosen to inject into the re-entrant honeycomb structure by injection molding to form the composite sandwich layers. The total bulletproof system was later constructed with the boron carbide ceramic plates and aluminum alloy plates. The mechanical behaviors and energy absorption characteristics of different composite sandwich layers were investigated by quasi-static and dynamic compression tests. The dynamic responses of different structured layers were analyzed via numerical simulations in ANSYS/LS-DYNA, which employed 7.62 mm projectiles. The results indicated that the injection-molded composite sandwich layer shows excellent compressive strength and energy absorption capacity. The bulletproof performance of the injection-molded system has been greatly improved comparing with the non-injected molded system. Compared with TPU and PP, the composite injected with PC presents optimal penetration resistance.