This paper is a design and experiment about the radar’s circular polarization in the Kuband. Since the proposed method used Post to that it could manufacture the circular polarization antenna by using the linear antenna it could reduce the structural size of an antenna. 3 Posts were used in order to broaden the Axial ration Bandwidth of the circular polarization antenna. A distance between Posts and Post length were appropriately selected for the axial ratio optimization and applied in the design. The designed antenna was confirmed that it has the axial ration optimization and applied in the design. The designed antenna was confirmed that it has the axial ration BW of 12.7% and gain of 7.8dBi.