The surface wave loss in the patch antenna reduces the bandwidth and gain of the patch antenna. This problem is overcome by use of frequency selective surface. The FSS screen design with 1 slot is used for improving the gain of the antenna at frequency 9.1GHz. Gain improvement of about 2db is achieved. The reflection characteristics of the FSS are used to improve the gain of the patch antenna. The FSS screen used here is showing the multi-resonant behavior.