In this paper, a lowprofile Superstratum Microstrip antenna with high gain and low RCS is designed. A metallic square loop loaded with resistors is mounted on the upper surface of the superstratum unit, which can absorb incoming radar wave to realize partly reflection. The integration of superstratum with the AMCbased antenna can greatly reduce the profile due to the partly reflection path of the superstratum and the inphase reflection property of the AMC. Meanwhile, the upper surface of the superstratum and AMC can generate a FabryPérot resonance to improve the radiation performance of the antenna. Through the integrated design of superstratum and the original antenna with the synthetic reflection AMC units on its upper surface, the patch on the upper surface of superstratum can generate a FabryPérot resonance cavity with AMC units on the upper surface of antenna, appliing to improve the radiation and scattering performances while reducing the profile. The simulation and measurement show that the |S11|<-10 dB bandwidth of the lowprofile superstratum microstrip antenna is from 13.8~15.36 GHz, while the gain is higher than that of the original antenna at least 3 dBi from14.40~15.42 GHz and its RCS is reduced significantly from 6 to 17 GHz. The 6 dB RCSreduction bandwidth is from 8.86 to 13.56 GHz and the maximum reduction is 14.8 dB.