Abstract: Objectives: Urban land development is shifting from horizontal expansion toward integrated use of above-ground, ground-level, and underground spaces. This transformation has produced mixed-use projects in which functions, property rights, shared interfaces, circulation systems, and governance responsibilities overlap in three-dimensional space. Conventional two-dimensional cadastres mainly describe parcel boundaries and land-use attributes in plan view, making it difficult to represent vertical stratification, cross-layer connections, public restrictions, and differentiated responsibilities. This study aims to construct a three-dimensional cadastre-supported spatial governance framework for mixed land use and to clarify how 3D cadastre can evolve from a tool for spatial representation and registration into a foundation for refined governance. Methods: The study combines theoretical analysis with case-based interpretation. Governance requirements are decomposed into compatibility, capacity, and externalities. A spatial property-right representation framework is then constructed through 3D spatial units, interface relations, and connectivity networks. On this basis, a configuration system of rights, restrictions, and responsibilities (RRR) is developed to associate spatial objects with right holders, public constraints, and governance duties. Cases of rail-transit overbuild development, vertically differentiated land supply, and underground transport hubs are used to explain the framework. Results: The framework consists of three dimensions. At the functional level, 3D cadastre provides a spatial basis for identifying and verifying compatibility, capacity, and externalities. Compatibility is assessed through the extents, interfaces, shared areas, and connections of different uses. Capacity control is linked to spatial units, corridors, vertical transport facilities, and transfer nodes, while professional assessment results are attached to identifiable spatial objects. Externalities such as noise, vibration, lighting, traffic impacts, and pedestrian spillover are related to impact sources, transmission paths, and affected objects. At the spatial level, 3D spatial units define horizontal and vertical extents; interface relations describe adjacency, support, attachment, separation, and shared use; and connectivity networks organize corridors, entrances, transfer nodes, and emergency routes into a traceable topological structure. The Suzhou East Railway Station case illustrates the conversion of vertically differentiated functions into 3D land-supply units, while the Gangxia North Transport Hub case demonstrates the representation of shared interfaces and multi-level circulation relationships. At the institutional level, the 3D RRR system links rights allocation, public restrictions, and governance responsibilities to specific property objects. At the institutional level, the 3D RRR system links rights allocation, public restrictions, and governance responsibilities to specific property objects. Rights can be associated with explicit 3D extents, while public-access requirements, facility-protection conditions, maintenance duties, and operational responsibilities can be recorded through registration notes, planning conditions, contracts, or management rules. These objects can be associated with right holders, right types, uses, public-access requirements, facility-protection conditions, maintenance duties, and operational responsibilities. Conclusions: The framework integrates functional governance, spatial property-right representation, and RRR configuration within a unified cadastral logic. Its contribution lies not only in adding vertical geometry, but also in organizing functions, spatial relationships, public constraints, and responsibilities around common 3D objects. This supports consistent links among planning control, construction verification, cadastral survey, property registration, and operational management. Future research should address quantitative governance evaluation, lifecycle data-conversion standards, and legal procedures for 3D registration and spatial representation of easements.