A smart city system, including: a functional system, a physical system, and an information system. The functional system is an expression form of functions of the smart city; the information system is an implementation way of the functions of the smart city; and the physical system is a physical support carrier for the implementation of the functions of the smart city. The functional system has a five-platform structure; the physical system has a five-layer structure; and the information system has a five-domain structure. Through the setting of these technical characteristics, a smart city system with clear system, definite functions, matching hardware, and clear information circulation can be constructed. The smart city system has a wide range of applications.