Smart city is a new type of urban form, which uses the new generation of information technology such as the Internet of Things (IOT) to achieve the city intelligent operation and management. It is the product of the integration of information technology and urban development. Based on the in-depth analysis of the problems facing the development of smart city, the basic concept of the city IOT infrastructure is presented, the development situation at home and abroad is analyzed, the key technologies of the city IOT infrastructure are put forward, and at last some suggestions for promoting the development of the city IOT infrastructure are proposed.