In the context of the transformation and upgrading of the construction industry, aiming at the problems of low management efficiency of large-scale building operation and maintenance process, insufficient accuracy of decision analysis of various operation and maintenance events, and the degree of management intelligence needs to be improved, this study proposes an intelligent operation and maintenance theory system and implementation method based on digital twins. Firstly, the information required for intelligent operation and maintenance of large buildings is summarized, and the problems to be solved in intelligent operation and maintenance are analyzed. The intelligent sensing technology is integrated into digital twins to propose operation mechanism of intelligent operation and maintenance, and the intelligent operation and maintenance architecture system for large buildings and the multidimensional and multi-scale twinning model are formed. Driven by the theoretical system, the realization method of building intelligent operation and maintenance is explored. It includes the collection and transmission of all elements of intelligent operation and maintenance information, the construction and operation of intelligent operation and maintenance twins, the management mechanism of intelligent operation and maintenance twin data and the architecture of intelligent operation and maintenance platform. Under the guidance of intelligent operation and maintenance theory system and implementation method, an intelligent operation and maintenance platform is formed and applied to the operation and maintenance management of a large construction project. By considering the virtual-real interaction and spatio-temporal evolution in the process of operation and maintenance management, the effectiveness of digital twins in improving the intelligence of operation and maintenance management is preliminarily verified.