Abstract-Cavity reflex antenna (CRA) employing a circular patch type FSS (Frequency Selective Surface) superstrate is investigated. Analysis in terms of gain, bandwidth (impedance and gain) and radiation pattern has been presented. The aim of this work was to study low profile CRA having very thin superstrate sizes. In this CRA a circular patch antenna is used as a feeding source. The circular patch type FSS possesses some unique properties favorable for thin superstrate sizes. In practice when the excitation source of the CRA is a probe-fed microstrip antenna with finite ground plane, substrate and superstrate, cross-polarization increases. In the presented design, the cross polar level has been reduced by choosing the optimum air gap and superstrate geometrical and electrical properties. A CRA with circular patch type FSS offers better performance both in terms of gain and impedance bandwidth for, thin superstrates (0.008λ 0 ) while giving a gain of 13 dBi and considerably reduced crosspolar level. The proposed antenna exhibit nearly equal E-plane and H-plane radiation pattern. Measurement results are provided to support the simulated results (by Ansoft HFSS). The circular patch type FSS is easy to fabricate and can be embedded into the host profile.