Based on the theory of polarization conversion, this paper designs and implements two electromagnetic units with 180-degree reflection phase differences in the range of 10-40 GHz. By coding and optimizing the spatial arrangement of the two basic units to obtain a metasurface, which makes the incident electromagnetic waves reflect diffusely and the energy in a single beam direction is reduced to realize the reduction of the Radar Cross Section (RCS). The full-wave simulated show that compared with a metallic surface of the same size, the RCS of the proposed metasurface can be reduced by more than 10dB in the two broadband bands of 12. , and the maximum reduction can reach 26 dB.