In this paper, we present a kind of broadband absorbent material. The broadband absorbent material is designed based on topology optimization and tested. The optimizing of metamaterials with a genetic algorithm has become one of the most effective methods of designing metamaterials in recent years. An integral system with interactive simulation of MATLAB and CST Microwave Studio is developed, and the main program of genetic algorithm is written in MATLAB; with simulation and computation in CST the metamaterial is optimized by a genetic algorithm with power of global optimization. Vacuum assistant resin infusion process is a new cost-effective and high-performance process. The proposed radar absorbent material possesses a sandwich structure, which consists of transparent composite skin panel, resistive metasurface, polyurethane foam and reflective composite skin panel. The transparent composite skin panel is low-dielectric-constant glass fiber reinforced composite, which has excellent physical properties and weather resistant property. The core material is composed of low density polyurethane foam and metamaterials, which can well meet the requirements for weight reduction and the invisibility. The reflective composite skin panel is a low-resistance carbon fiber reinforced composite, which prevents the electromagnetic waves from transmitting and also provides electrical boundary conditions for metamaterial. Simulation and test results indicate that the reflectivity of the radar absorbent material is less than-12 dB in a range of 2-18 GHz. Because of the symmetrical structure design of the resistance film, the radar absorbent material is polarization-independent. We preliminarily produce a batch of radar absorbent materials and test their various performances. Such a radar absorbent material has a strong absorption and other properties such as light quality, high temperature resistance, low temperature resistance, humidity resistance and corrosion resistance. The radar absorbent material which has been widely used in the engineering field is easy to achieve the compatibility of absorption, mechanical properties and environmental performance. Compared with previous design method, the topology optimization design is simple in programming operation, good in generality, and short in design periode. The radar absorbent materials owns strong application value.