Abstract: As an important form of wide-band dual polarization antenna,the four-arm sinuous antenna has been widely used in EW equipments.In this paper,the operation principle and design method of the four-arm sinuous antenna are discussed,and the main characteristics and potential application field of this kind of antenna are also introduced.Finally,this paper gives an example of a four-arm sinuous antenna working at 0.5 to 3 GHz.The test result shows that this antenna has excellent electrical performance in a 6:1 bandwidth.