The invention discloses a Fabry-Perot resonant cavity broadband high-gain microstrip antenna based on a single-layer double-sided coating structure, and belongs to the field of antenna wireless communication. The antenna comprises a bottom metal grounding plate, an antenna dielectric bottom plate, a U-shaped slot antenna radiation patch and an upper-layer single-layer double-sided frequency selective surface. The metal grounding plate, the antenna dielectric bottom plate and the U-shaped slot antenna radiation patch are seamlessly stacked, and the single-layer double-sided frequency selectivesurface is composed of a single-layer coated dielectric substrate, a square annular aperture structure and a cross grid structure. A U-shaped slot is etched on the metal patch of a traditional microstrip antenna, so that the bandwidth of the antenna structure is improved, the main radiation direction of the antenna is ensured to be right above the antenna structure, thereby meeting the design requirements of a Fabry-Perot resonant cavity antenna. Based on the above, the single-layer double-sided frequency selection surface model with positive phase gradient is designed, and the gain bandwidthof the Fabry-Perot resonant cavity antenna is increased. The method is simple in design, is easy to understand, is wide in application range, is high in portability and is suitable for the characteristics of high gain and broadband of the Fabry-Perot resonant cavity antenna.