Abstract: Most broadband microstrip antenna are implemented in the form of slot structure or laminate structure. The impedance bandwidth is broadened, but meanwhile the sidelobe of the directivity pattern and backlobe level are enlarged. Therefore the performance is degraded, which confines the application of the microstrip antenna. A broadband stacked slot coupling microstrip antenna array with EBG structure reflector is proposed. The minimized metal EBG reflector possesses a feature of high impedance surface.Compared to the conventional reflector structure, the fronttoback ratio improved 1.29dB, the maximum backlobe level is reduced by 3.16dB. The distance between the antenna and reflector is shortened to 14mm (<λ/4), and the antenna profile is lower.Test results indicate that, the proposed reflector structure can effectively improve the directivity pattern of stacked antenna and aperture coupled antenna, promote the fronttoback ratio, and reduce the thickness of the antenna.