Smart city is an inevitable development trend in the future, which has a strong role in promoting urban development. Promoting the construction of smart city can not only improve people’s living standards and quality of life, but also effectively promote urban development. This paper first gives an overview of smart city, then briefly introduces the characteristics of smart city, and finally analyzes the key supporting technologies and applications of smart city construction, including cloud computing technology, big data technology, Internet of things technology, artificial intelligence technology and 3D Printing technology. Smart city is a new urban form. In the process of building a smart city, the core is the key supporting technology. Therefore, it is necessary to strengthen the research on the key supporting technology and combine it with the actual situation of the city to achieve effective use.