Abstract: This paper studies a Ku-band rectangular radial line sub-array feed system. In order to meet the requirement of specific coupling, this paper proposes a new type of coupling probe with superposition structure, and on this basis, the center frequency of 12.5 GHz 28 unit sub-array rectangular grid radial line feed system is designed and analyzed. Simulation results show that: The diameter of 61.6 mm125.2 mm feed system in the center frequency of 12.5 GHz has a reflection coefficient of 0.015, and a roughness of 1.05 dB. At the same time, within the scope of 12.2-12.7 GHz frequency band, the reflection coefficient is less than 0.1, and the maximum roughness of amplitude is 2. 62 dB, and the feed system basically meets the requirements of continuous feed output for 28 ports.