Abstract: A side-feed offset Cassegrain (SFOC) antenna is studied. The influence of structural parameters on the radiation pattern of the antenna is discussed. The optimal beam scanning of the antenna is achieved by adjusting the antenna design parameters. The radiation pattern of the antenna at different scanning angles is calculated. The changes of the sidelobe level and antenna gain during beam scanning are analyzed. The simulation result shows that except for the case where the feed is blocked by the reflector, the gain loss and the sidelobe level variation of the SFOC antenna are small, which provides a reference for the design of the satellite antenna.