Abstract: In recent years, the reduction of Radar Cross Section (R,CS) for antenna has been an important topic in the field of electronic warfare. The way to reduce the RCS of bi-reflective antennas, which have been widely used, in the axial direction is discussed in this paper. The conclusion shows that reasonable selections of the focal distances of the main reflector may be able to obtain low RCS, keeping the high-gain under the antenna unchanged.