Abstract: A broadband dual polarization shared folded arm antenna is proposed for L and S-band dual polarization signal broadband monitoring. The antenna adopts width changing arms and a shared folding branch structure. This design widens the relative bandwidth of the antenna from 57.78% to 85.7%, and improves the problem of pattern splitting in the high frequency band of the antenna. Theoretical and experimental result show that the voltage standing wave ratio(VSWR) of the antenna is less than 2.0 in the frequency band of 1.6−4.0 GHz, the typical gain is 8.3 dBi, and the size of the antenna is only 28% the wavelength corresponding to the lowest frequency. The proposed antenna can be applied to broadband dual polarization monitoring system of communication signal.