An antenna RCS reduction method based on double M-type polarization conversion metasurface is proposed in this paper. Firstly, a wideband polarization conversion metasurface element is designed, which is characterized by high efficiency, simple structure and good performance. The PCM cells are arranged to form a low RCS metasurface array, and used in patch antenna and patch antenna array, and the results show that the tessellated low RCS metasurface is applied to the above antennas, which can achieve RCS reduction within the 12–30 GHz band while guaranteeing the radiation performance of the antenna.