Optical satellite communication has advantages over the RF satellite communication in capacity, speed, secrecy and anti-interference.Space information superhighway composed of GEO/MEO/LEO satellites which are linked by optical inter-satellite links(OISL) would play important roles in communication, navigation, martial recon, remote sensing and deep space exploration.A novel LEO/MEO two-layered optical satellite network with global coverage is designed with the street-of-coverage technique.The layer of LEO satellites is the walker-delta constellation with zero phase factor and has the quasi-stable logical structure of Mesh.Equatorial and polar orbit satellites constitute the layer of MEO satellite, which can cover LEO layer effectively.Rising satellites of the system can provide 99.9% of coverage for the whole globe and 100% for China averagely.The network can provide a minimum elevation angle at 21 ? with single-satellite visibility for China, and at 16 ? with the dual-satellite visibility.Simulation results of the inter-satellite links show LEO constellation of zero phase factor outperforms non-zero phase factor constellations in azimuth angle, elevation angle and distance, which is very fit for the OISL.Simulation results of the communication performance indicate a little difference between short wave band and long wave band at low communication speed(several Gbit/s);however, the wave band at 1550 nm is a better choice at high communication speed(100 Gbit/s). Optical satellite communication has advantages over the RF satellite communication in capacity, speed, secrecy and anti- interference. Space information superhighway composed of GEO / MEO / LEO satellites which are linked by optical inter-satellite links (OISL) would play important roles in communication , navigation, martial recon, remote sensing and deep space exploration. A novel LEO / MEO two-layered optical satellite network with global coverage is designed with the street-of-coverage technique. The layer of LEO satellites is the walker-delta constellation with zero phase factor and has the quasi-stable logical structure of Mesh. Equatorial and polar orbit satellites constitute the layer of MEO satellite, which can cover LEO layer effectively. Handing satellites of the system can provide 99.9% of coverage for the whole globe and 100 % for China averagely.The network can provide a minimum elevation angle of 21? with single-satellite visibility for China, and at 16? with the dual-satellite visibi lity. Simulation results of the inter-satellite links show LEO constellation of zero phase factor outperforms non-zero phase factor constellations in azimuth angle, elevation angle and distance, which is very fit for the OISL. Simulation results of the communication performance indicate a little difference between short wave band and long wave band at low communication speed (several Gbit / s); however, the wave band at 1550 nm is a better choice at high communication speed (100 Gbit / s).