Smart City is a new concept that uses Information and Communication Technology (ICT) to promote the smartification of urban construction, planning and services. Currently, a number of countries and cities have conducted studies on Smart City, but they mostly focused on the conceptual connotations analysis and applications in specific domains, lacking a common, shareable and integrated framework understanding, which led to significant barriers among individual Smart City projects. By analyzing the framework connotations and application domains of Smart City, this paper proposed a common, shareable and integrated conceptual framework for smart city. Then based on this framework, a unified portal platform that is suitable for multiple domains, including the government, citizen and business, as well as common, custom and other application modes, is further proposed. Finally, Smart Weifang was implemented based on this platform. The application outcomes indicate that this common and shareable platform can effectively eliminate the data and technological barriers between different smart city systems, while also avoiding redundant financial investments. The investigation of the proposed framework and platform is of key significance to the unified construction of Smart City and the intensification of the hardware environment, thus representing a true achievement in the transition from “information island” to “information sharing and interconnection” for urban informatization.