Recently, the electromagnetic band-gap (EBG) material, also known as photonic crystals, has been successfully used to suppress surface-wave for the patch antenna. In this article, a sectoral horn antenna with the mushroom-like EBG material is designed to enhance its gain. A flange plate is attached to the horn antenna mouth and a mushroom-like EBG material is sticked to the flange plate. Because of effective surface-wave suppression, the simulant and test results show that the gain of this sectoral horn antenna has almost increased 1.0 dB within the frequency front 11.7 to 14.0 GHz. This kind of horn antenna has the potential application in mobile and satellite communications. (C) 2008 Wiley Periodicals, Inc.