Development zones are special functional areas oriented towards economic development efficiency that were established after China’s reform and opening up. Serving as phased policy objectives, China’s development zones have largely adopted the governance structure of management committees, coexisting and intertwining with administrative divisions organized according to administrative principles, forming a unique “dual-track” spatial governance model. Against this backdrop, the mechanism of administrative districts entrusted to development zones has emerged, which delegating the economic and social management authorities of specific regions originally belonging to different administrative districts to a management committee of a development zone without altering the administrative divisions. It serves as a transitional and informal institutional arrangement. This governance model has largely addressed the issue of insufficient development space in development zones, expanded their authority to allocate spatial resources, and consequently enhanced the efficiency of industrial development. However, as this model has become more widespread and entrenched, conflicts between development zones and administrative districts in spatial governance have gradually emerged, affecting the optimization of the overall urban spatial layout and the improvement of governance performance. Studying the typical spatial types, mechanisms and motivations, spatial governance conflicts, institutional costs and benefits of the administrative trusteeship model in development zones is of significant importance for enhancing the institutional optimization of development zones and the spatial collaborative governance effectiveness between development zones and administrative districts.Firstly, based on observations from the case of Xi’an, the study identifies two main modes of administrative trusteeship in development zones. One is the complete trusteeship model, where certain administrative districts are stripped from their original administrative divisions and fully entrusted to the development zone for comprehensive management. The other is the incomplete trusteeship model, where administrative districts delegate their economic and industrial development functions to the development zone, while retaining social governance functions within the administrative district government.Secondly, the study analyzes the inherent motivations for administrative trusteeship in development zones. From the perspective of prefecture-level governments, the trusteeship model can promote local economic development in terms of industrial development planning, investment attraction, and service enterprises. From the perspective of the management entities of development zones, getting more administrative space is conducive to obtaining greater land development rights and achieving a new round of spatial growth. Thirdly, this study analyzes the spatial governance conflicts arising from administrative trusteeship in development zones, mainly including three aspects. 1) From the perspective of local economic development, the large-scale administrative trusteeship will strengthen the plate boundary between the development zone and the administrative district due to the large difference in the level of industrial development between the development zone and the administrative district, the siphon effect of the development zone on the unmanaged areas of the administrative region will be intensified. 2) Fromthe perspective of overall spatial governance, the strengths of development zone administrative committees lie in planning, construction, and industrial development, but they have shortcomings in terms of capacity building and experience in social space governance. Limited by institutional and personnel configurations, administrative committees of development zones lack the necessary governance capabilities for ecological and agricultural spaces within the entrusted areas, leading to the emergence of governance blind spots. 3) From the perspective of planning formulation and approval, the lack of territorial spatial planning and compilation authority in development zones may result in insufficient planning coordination in boundary areas, insufficient overall planning among functional platforms, and an increasing trend of fragmented land use.Finally, the study explores the evolutionary trends of the trusteeship mechanism in development zones from the perspectives of governance costs and institutional benefits. 1) From the perspective of trusteeship scale, the benefits of trusteeship during the incremental expansion period can generally cover its governance costs. Conversely, blindly expanding the scale of trusteeship in the stock era will significantly increase the governance costs of newly added spaces, making it difficult to cover their benefits. 2) The trusteeship mechanism can effectively promote the development efficiency of growing development zones; however, mature development zones should consider promoting the “administrativization of development zones” and shifting the focus of spatial governance from industrial development to the integrated development and fine-grained governance of overall production, living, and ecological spaces. 3) From the perspective of the location and functional types of development zones, those that have been highly integrated with cities and transformed into comprehensive urban areas should abolish the trusteeship mechanism. Specialized development zones located on the outskirts of cities and focused on industrial production still need to retain the trusteeship mechanism for a certain period.