CIM is a fundamental platform software for the construction of smart cities and realistic 3D China with the technical advantages in mobile measurement, spatio-temporal informatization, lean Big Data and artificial intelligence. The platform based on "BIM+GIS+IoT", integrates IoT perception data and multi-dimensional spatio-temporal data including above and below ground, indoor and outdoor, history, present and future, which builds an organic complex of city information in 3D digital space, which provides the ability to simulate from building single unit, community to city level through the management and visualization of city 3D model, servicing for the construction and operation of applications in smart cities. In addition, the platform follows the standards related to cloud platforms and allows access to infrastructure platforms such as government clouds to realize common construction and sharing.