Quantum safety communications is a process of quantum key distribution （QKD）. Current QKD technology restricts transmission to a low bit rate. To improve the QKD bit rate and develope high rate and large capacity, we propose a multiple-input-multiple-output（MIMO） quantum key distribution system. The Wigner operator of multi-photon entangled states in MIMO quantum key distribution channel is presented. As a result, the Wigner function of multi-photon double-model squeezed entangled sates and MIMO quantum key distribution channel capacity are also obtained, which will provide theoretical support and technical basis for developing robust space-time processing algorithm of MIMO quantum safety communications and designing optimum high performance system of MIMO quantum key distribution.