Abstract: A simple but high efficient approach of reducing the mutual coupling is proposed for dual-element cavity-backed slot antennas using hybrid reducing mutual coupling method. By inserting two symmetrical parasitic elements and removing part of the substrate between two coupled slot antennas, the mutual coupling reduction of 9. 7dB is achieved in the bandwidth of 1. 7% (at the central frequency of 12GHz) with reflection coefficient less than -10dB through the optimization for single frequency. Meanwhile, radiation patterns are improved than those of normal antennas and end-fire radiation is reduced. Based on the optimization for single frequency, the mutual coupling is improved through the optimization in the bandwidth, the mutual coupling reduction of 11. 5dB is achieved in the bandwidth of 2. 2% with reflection coefficient less than -10dB. The features of this hybrid method include very simple structure, low cost, easy fabrication.