Cities are stable physical and social space that serves human agglomeration activities and takes shape with the force of human being on natural conditions. Cities are made up by urban population (people chose to live together and pursue opportunities for physical contacts out of rational choice), people’s activities and environmental facilities (space agents and municipal government). Besides the stable location that distinguishes it from non-urban residential areas, cities have three inter-connecting characteristics of agglomeration, connection and sharing, which not only distinguishes cities from non-urban areas, but also determines the meaning, function, scale and form of the cities themselves.