Abstract: In order to improve the radiation uniformity of reflector antennas, an offset reflector antenna working at 15 GHz is designed by using a beam-forming technology. The reflector antenna consists of a non-uniform rational B-splines(NURBS) reflector and a dielectric rod antenna, and the reflector surface is shaped by using both the physical optics and the Nelder-Mead algorithms to obtain a desired radiation pattern. The simulation results show that the relative side lobe levels of the shaped reflector antenna are below -20 dB, the gains in the beam width of -2.7° to 2.7° are exceed 20 dBi, and its fluctuation does not exceed 1 dB. This antenna has the characteristics of simple construction, low side-lobe and uniform gain, which plays an important role in satellite communication.