Abstract: Annulus metallic material (AMM) is used in microstrip antenna to achieve low radar cross section(RCS) property in a wide frequency band.The structure is composed of several concentric annuluses.By placing the metallic annuluses around the radiation patch of the reference microstrip antenna, wideband monostatic RCS reduction is achieved.The results indicate that the proposed antenna possesses obvious RCS reduction from 6 GHz to 25 GHz for both x- and y-polarized vertically incident waves.The maximum reduction is achieved at 12.8 GHz for as much as 30 dB and the radiation performance of the antenna is well preserved.