The honeycomb absorbing composites with light weight, high strength and broadband absorbing property had been designed by combination of aramid honeycomb and lossy frequency selective surface composite. The effect of the thickness of honeycomb and the configuration of lossy frequency selective surface on electromagnetic performance was investigated, while the electromagnetic absorbing principle of the lossy frequency selective surface with traditional aperture was analyzed by the equivalent circuit method, and of which the deficiency in broadband absorbing was also proposed. In order to resolve the structure with none equivalent capacitance, slots were made on the lossy frequency selective surface with traditional aperture. Consequently, there have been another absorption peak in low frequency, and the high frequency absorption performance kept unchanged. Correspondingly the low frequency absorption performance was greatly improved, thus the whole absorbing performance of the very configuration was greatly improved, and the absorbing bandwidth had been broadened more than one time. Through calculating the equivalent capacitance and inductance by matlab, it follows that as the width of square ring changed,the equivalent inductance varied accordingly,but the equivalent capacitance remain unchanged; The high frequency absorption peaks were mainly affected by the equivalent inductance, and the low frequency absorption peaks were mainly affected by the equivalent capacitance. The thickness of honeycomb mainly affected the low frequency absorption peak and the position of high frequency absorption peak. According to the above characteristics, a thickness of 6mm broadband honeycomb absorbing composites had been designed with the slotted lossy frequency selective surface in front of the honeycomb medium, which presented an absorbing bandwidth 14 GHz of -10 dB. The actual test result basically accorded with the design expectation.