The invention discloses a multilayer broadband microstrip antenna, comprising an upper dielectric baseplate, a middle dielectric baseplate, a lower dielectric baseplate, an upper low dielectric constant insulating dielectric layer, a lower low dielectric constant insulating dielectric layer, a reflection plate and a feed probe, wherein rectangle radiators of metallic copper pasters are arranged on the lower surface of the upper dielectric baseplate and the upper surface of the middle dielectric baseplate and provided with U-shaped slot structures with different sizes respectively. Due to a special double-layer inverted U-shaped slot coupling feed way, the symmetry of directional diagrams on an E surface or H surface of the antenna is good, thus ensuring that the antenna has more consistent performances in more directions, and having more actual meanings as an exploration antenna and a communication antenna. The reflection plate with an EBG (electromagnetic band gap) structure can preferably restrain backward radiation in the specified frequency relative to a traditional metal reflection plate, thus improving the directivity of the antenna, thereby further improving the gain of theantenna.