A high-gain antenna with wideband low radar cross-section (RCS) property using polarization conversion metasurface (PCM) and partially reflecting surface (PRS) is investigated. PCM and PRS are printed on two sides of a substrate, above the microstrip patch antenna to form Fabry–Perot (F-P) resonant cavity. Due to the symmetrical arrangement of PCM unit and its mirror unit, remarkable wideband radar cross-section reduction (RCSR) is obtained in both x- and y-polarizations. Simulated and measured results show that combination of PCM with PRS antenna contributes to significant in-band and out-of-band RCSR, as well as 7 dB gain enhancement. Wideband RCSR ranging from 9 to 20 GHz with maximum in-band value is 20 dB at 9.4 GHz, and 33 dB out of band verified its superiority in RCS control.