The existing is difficult to meet the channel spacing of the RF frontend of the satelliteborne multibeam phased array antenna. The existing research work focuses on improving the integration of RF circuits and chips. A sparse array is proposed to increase the average spacing of the antenna elements, so as to alleviate the highdensity integration problem. The sparse array of Kaband eightbeam phased array antenna is designed. Firstly, genetic algorithm is used to optimize the 64element sparse subarray, and the subarray gain is greater than 18.6 dB over the ±60° scanning range. The subarray is mirrored symmetrically along the four quadrants, which is convenient for the efficient design of the stripline transition board that interconnect the irregularly distributed antenna unit ports with the regularly arranged R module ports. Then 36 subarrays are randomly rotated and translated to form the full array. To some extent, the distribution uniformity of the subarray is disturbed to suppress the grating lobe. The method proposed is simple, efficient and fast. The design results of sparse array can basically meet the requirement of engineering applications, and is suitable for satelliteborne multibeam phased array。