Full-duplex has a great promotion for channel capacity compared wit h half-duplex, but the interference of relay and the leakage between multi-user affect the performance of communication system. We combine null-space projecti on(NSP) algorithm used to restrain the self-interference with zero forcing(ZF) and block diagonalizat ion(BD) algorithms used to cancel the interference between different users to restructure beamforming matrix es, thus canceling the selfinterference and multipair interference in multi-user full-duplex two-way relay system with decode-and-forward(DF) strategy. Simulation results reveal that the multi-user full-duplex two-way relay system can restrain the selfinterference of relay and the interference between multi-user at the same time.