Smart city is a new concept and model of urban development, and it is the combination of urbanization development and the new generation of information technologies such as Internet of Things, cloud computing, mobile network and big data. With the explosive growth of the quantity of data in cities, how to share and fuse the massive, heterogeneous, multi-source data in smart city becomes a core issue which must be solved. In this paper, the characteristics and drawbacks of traditional data sharing and fusion technologies are firstly described and analyzed in details, and then some frameworks and thoughts such as semantic Web, data vitalization and Internet of data, which may resolve the data sharing and fusion problems in smart city, are introduced. Based on these studies, a new framework of data sharing and fusion in smart city—smart city linked data framework is proposed. Then the overall layered structure, advantages against the other relevant frameworks and technologies are described briefly. Next, the functions, technologies and challenges of each layer are described in details. The concept of data semantic annotation tag (DSAT) are proposed. And the technologies, methods and classifications of DSAT are described in details. At last, the relevant issues about data linked layer are analyzed in details.