Abstract: A metasurface with dual characteristics of absorbing/transmitting waves is designed and used for the superstrate of microstrip antennas to realize the wideband reduction of the radar cross section (RCS) of the antenna. In this paper, the metal unit of metamaterials absorber is replaced with tantalum nitride material to increase the absorbing bandwidth. At the same time, the combination of the absorbing material and the frequency selective surface is realizes. The superstrate has two completely different electromagnetic characteristics of absorbing/transmitting when the electromagnetic waves irradiate in different directions. The superstrate is placed above the antenna, and when the antenna is working, the electromagnetic waves radiated by the antenna can pass through the superstrate perfectly, so the radiation characteristics of the antenna will not be affected. When the electromagnetic waves irradiate the antenna, the broadband absorbing characteristics of the superstrate can minimize the RCS of the antenna. The results show that when the absorbing/transmitting metasurface designed in this paper is used as the antenna superstrate, the radiation characteristics of the antenna hardly change, and the maximum reduction of the monostatic RCS of the antenna can reach more than 20 dB, and the reduction bandwidth is 5−19 GHz. At the same time, the monostatic and bistatic RCS of the antenna have also been significantly reduced in a wide angle range.