Abstract: A multipath routing algorithm is proposed for space information networks on the basis of a deep interview to its characteristics. In the algorithm, a space information network topology is divided into backbone and non-backbone. Since the motions of backbone nodes are periodic and predictive, routs between them are statically configured. In the static configuration, each node is assigned a selection factor that indicates the probability to be selected in a certain route, which effectively avoids network bottleneck. Routs containing non-backbone nodes as a part are generated on demand for dramatic change of non-backbone topology, which makes overhead of rout maintaining under tight control. Multipath routing is constructed adaptively according to network environment, and a load balance mechanism is also designed to balance load among multipath. Rout maintaining automatically operates on the change of topology, which improves autonomous ability of the network. Simulation results show that the proposed algorithm has a fast convergence speed with little cost, and improves network processing ability, which indicates the algorithm well suits space information networks.