Abstract: Co-construction, co-governance and sharing is China's fundamental social governance system, which coexists with the development process of China's social governance modernization, and embodies obvious cooperative requirements and public characteristics. In the form of a fundamental system, the state has solidified joint construction, governance and sharing into a development idea for the modernization of social governance. Co-construction, co-governance and sharing covers three-dimensional logic of analyzing and resolving problems in the field of social governance. Co-construction lies in the main dimension of social governance, and the modernization of social governance system answers "who depends on social governance"; co-governance refers to the path dimension of social governance, modernizing the way of social governance explains "what to do with social governance"; sharing means the value dimension of social governance, and the answer to "who is social governance for" is to establish a community of social governance.