Significant progress has been made in satellite-based quantum key distribution (QKD), and urgent follow-up work is to explore the optimal solution for building practical quantum constellations. Here, we demonstrate successful QKD based on the compact terminal on the Tiangong-2 Space Lab and construct a space–ground quantum network among four ground stations. The medium-inclination orbit of Tiangong-2 Space Lab can obtain multiple available passes for the same ground station in one night, increasing the key generation amount directly. Further analysis results show that the medium-inclination orbit and Sun-synchronous orbit can form good complementarity in future quantum constellations. As a comprehensive demonstration, this work takes a step toward cost-effective quantum satellites and provides a perspective for satellite constellation construction with different orbit types.