Abstract: To reduce the weight of the dual-polarized quadruple-ridged horn antenna over the frequency range of 75-500 MHz, a composite sandwich structure is used to build the antenna, which comprises solid aluminium and honeycomb materials. The parameters of structure are optimized by Ansoft HFSS software, and an adjustable shorting plate is put at the bottom of the antenna to prevent the occurrence of singularities created by standing waves. A modified Teflon board is inserted into the interspace between the four symmetric ridges. Both simulation results and measurement results show that the satisfied impedance and pattern characteristics for interested bands are obtained.