The heterogeneity of mega constellations is a market-driven and mission-driven trend of space-based systems in the future，and how to develop，use，and manage heterogeneous mega constellations well is a hot topic of continuous discussion in the industry. In view of the problems of heterogeneous mega constellations in system design， collaborative networking， flexible application， and system operation， in this paper， the construction concept of a seven-in-one heterogeneous mega constellation system of“interconnection，perception， intelligent calculation， express transport， research & verify， manage & control，and convenient application” is proposed， aiming at the requirements of “dynamic collaboration，high-quality service，seamless service， and easy control”.The open design concept is adopted to realize fast，flexible，and independent constellation resource integration and scheduling. he system supports modularization， scalable multi-missions， and multi-application on-demand services.