In the context of information warfare, stealth technology is a critical aspect of military capability development. Reducing radar cross section (RCS) has profound implications for stealth technology. Antennas, as a special type of scatterer, require RCS reduction while maintaining good radiation performance. In recent years, the emergence of metasurfaces has provided more possibilities for the development of antenna RCS reduction. Electromagnetic metasurfaces have significant application value in polarization control, beam steering, and radar target stealth. By designing the structural dimensions, shapes, and periodic arrangement of each unit, metasurfaces can achieve low-scattering characteristics. Integrating metasurfaces with antennas in a unified design can achieve good RCS reduction with minimal impact on antenna radiation performance, which holds great promise in the field of antenna stealth. In this paper, using Ansys HFSS software for modeling and simulating metasurfaces, we propose and verify a polarization conversion unit based on the venation structure of insect wings, maintaining a high polarization conversion rate. The polarization conversion units are arranged in a chessboard pattern to form a polarization conversion metasurface (PCM), ultimately achieving the RCS reduction in the 5.5–9.0 GHz without affecting the radiation function of the antenna.