With the success of commercial spaceflights, space information infrastructure (SII) has received much attention in recent years. Blueprints such as the low earth orbit global communication network and the data center in space have been proposed. To these ends, a satellite backbone network (SBN) is an essential part of SII and can connect multiple heterogeneous space networks, provide high-throughput connections for other space information devices, and even provide space computing power. To obtain ultra-high bandwidth and resource flexibility over limited channels, we propose a timeslot-based optical switched SBN (OSBN). More specifically, we show the node structure, switching system and bandwidth-on-demand (BoD) mechanism of the proposed OSBN. By simulation, we analyze the OSBN’s performances under different designed parameters and suggest the best ones. In addition, the BoD mechanism is verified to enhance differentiated service-of-quality. Experimentally, we demonstrate the access and handover processing of OSBN. Additionally, we analyze the performance of space computing over an imitated OSBN platform.