The invention provides a reflecting surface antenna double-beam forming design method. Through creatively introducing a double-beam covering area shape characteristic analyzing step in a designing process, a targeted initial beam acquiring manner and a corresponding antenna structure configuration strategy are made. Based on searching of a reflection plane scattered field focusing point under planar wave excitation according to a conjugate field matching theory, a rotation rule in long axis direction of a longitudinal movement beam of feed sources at two sides of a focusing point is utilized, and wave beam covering matching design is performed. Through feed source position adjustment, axial torsion of the whole reflection surface antenna system is performed, thereby improving beam covering matching property of double beams and performance of a restraining area, and furthermore improving gain of a double-beam coverage area after optimization. According to the reflecting surface antenna double-beam forming design method, according to a wave beam shape characteristic relationship, antenna layout and the like, and design principles such as a wave beam shape is adjusted according to the feed source position. A design order, a parameter selecting principle and technical details in double-beam design are described, and gain improvement of the double-beam coverage area is realized.