In recent years, the application of new technologies like big data, cloud computing, and artificial intelligence to the construction of ″Smart Cities″ has been developing fast. However, there are common problems, such as the mismatch between project construction imperatives and residents’ needs, lack of information-sharing mechanisms between stakeholder departments, and poor collaborative governance among multiple project entities. Some smart city projects have also become political, rather than social achievement projects. Consequently, most smart city construction outcomes have failed to play an effective role in combating the epidemic, or to help realize the transformation of modern social governance. By attribution logic, we start from the basic point of how a smart city can help modernize the system and capacity of social governance, and build a logical framework for a smart city oriented toward social governance.This empirical study of the Hangzhou City Brain,aims to analyze and clarify, how a technology-driven smart-city construction process can lead to efficient and precise governance, and force a decentralized and flat governance process to ultimately reshape a multivariate collaborative governance structure. The paper also proposes the orientation of a smart-city in the service of social governance in order to provide insights for smart cities to contribute to modern social governance. From control of traffic congestion to comprehensive control of diverse city functions, Hangzhou City Brain is a new digital infrastructure for urban development and a new platform for digital urban governance relying on an innovative centralised organizational structure, which is an important support for social governance systems. In the light of social governance modernization, a smart city is not only the pursuit of ″technical rationality″, but also a vision of a good governance ecology. This means ″co-building, co-governance and sharing″ to lessen the rigidity of governance processes and provide powerful tools to reconcile contradictions between the growth of governance capacity and the responsiveness of governance systems to support the construction of smart cities that help modernize social governance. We propose that a smart city’s contribution to social governance lies in three dimensions: (1) governance effectiveness, the interconnection of government departments and real-time data online which can bring efficiency of public policy implementation and improved precision of public service supply by reducing public service costs and fragmentation; (2) governance process, where the government is forced to flatten, decentralize, transform, and reshape its social governance processes by clarifying the public data resources of various government departments and reorganizing the pattern of social interests; (3) governance structure, the network pattern of multi-subject co-governance and multi-power orientation is created by adhering to the principal position of the People, and multiple collaborative governance. We supply this contribution toward the future orientation of smart cities: (1) in the context of the government's control of resources and technologies, it is necessary to prudently rely on institutional design to deal with the relationship between multiple governance entities in order to build a governance system guided by public values rather than administrative efficiency; and (2) in order to further promote the modernization process of social governance through operation and maintenance of smart city systems to realize the long-term governance capacity of public policy implementation and public service supply.