ABSTRACT:Horn antenna is flaring of open end of the waveguide. It is most widely used antenna at UHF and at microwave range. These are widely used transmitting and receiving antenna in the laboratory. Horn antenna provides a gradual transition of EM energy to the free space and prevent reflection of energy. The horn antennas are not always of small size, the world's largest conical horn antenna is about 14 feet.In this review paper, various techniques of antenna have been proposed. This paper is a review for optimization of gain performance of an antenna. The different type of material has different effects on horn antenna. The Particle Swarm Optimization technique is also discussed here to optimize the results.