Free-space quantum communication with satellites opens a promising avenue for global secure quantum network and large-scale test of quantum foundations. Micius Quantum Science Satellite was launched in August 2016 and many experiments have been achieved at space scale. To realize the truly global quantum network, there are still many difficulties and technical challenges to be pushed in the future. In this talk, I will introduce some of our efforts towards a practical space-ground integrated quantum communication network, such as quantum constellation with LEO nano-satellite, and the MEO/GEO quantum satellite. With the help of high-orbit quantum satellites, we may also conduct research on high-precision optical frequency standards and quantum effects in gravitational fields.