Space information network includes multi-system integration that involves real-time acquisition, transmission, and processing over the information systems. Space information network is an important strategic direction of China’s 13th Five-Year Plan for the innovation of science and technology, which is also considered to be the current focus area of national development. Efficient carrying and the information integration amongst different information services are the major challenges in the space information networks, which are constantly affecting the performance of system integration. Motivated by these challenges, in this paper, a Space Information Service (SIS) forwarding mechanism is proposed that is completely based on Software-Defined Network (SDN). According to the complexity of the information service demand, the designing of label tunnel control mechanism and packet/label mixed forwarding methodologies were executed by referring the concepts of SDN. Simulation results revealed that the SIS could efficiently achieve high information traffic delivery along with the management of the network tunnel.