In order to research media access control(MAC) protocol in deep space optical communication backbone networks, the structure of deep space optical communication backbone networks is designed, and a flat wireless Mesh structure for deep space optical communication backbone networks is also proposed. Due to the sensitive characteristics of laser communications, this paper designs the node model with multiple interfaces, and the directional media access control(DMAC) protocol is proposed. Compared with non-directional media access control(NDMAC), DMAC protocol can effectively improve the performance of network.