Space backbone network is an integrated network composed by the space-air-ground largescale backbone nodes, and the core of supporting space information network. On the basis of analyzing the status quo of research on space information network of the Europe and the United States of America, space backbone network architecture and protocol framework are proposed according to the relevant characteristics and overall requirements. The network is composed of spacebased network, airbased network, and groundbased network. By so doing, this realizes mutual communication and cooperation through intersatellite links, satelliteair links, satelliteground links, airtoair links, airground links and terrestrial communications lines. The spacebased backbone network based on multilayer satellite network and airbased backbone network based on wireless mesh are mainly studied. Finally, the paper explores the key technologies such as network structure, routing protocols, data transmission technique, heterogeneous compatibility, and network management. This research has some contributions for reference at a certain degree to the construction of future space backbone network.