Abstract: Self-interference from the relay transmission to reception in full-duplex MIMO relays reduces the channel capacity and has a negative effect on the relay performance. Theoretically speaking, the core problem of full-duplex MIMO relays is self-interference suppression. In this paper, we propose a novel technique for self-interference suppression. The relay employs transmit and receive weight vectors for suppressing the self-interference signal. Unlike the existing technique that is based on the singular value decomposition. Maximizing the ratio between the power of the useful signal to the self-interference power at the relay reception and transmission and forming a criterion function for jointly calculating the optimal receive and transmit suppression vectors, respectively. Simulation results confirm that the proposed scheme improves the channel capacity and mitigates the self-interference significantly.