In the design process of some scatter communication antenna, the feed is simulated and devised with high frequency simulation software (HFSS). The far field property of feed is fitted and interpolated, and the directivity pattern of the whole antenna is calculated combining uniform geometrical theory of diffraction (UTD). Through measuring the practical antenna, the results are consistent well, which proves that the hybrid method is of great precise and high speed in the analysis of this kind of antenna. And the method shows a tremendous application space and prospect in the engineering design.