Abstract: With the transformation of economic and the gradual promotion of new-type urbanization, county-level cities on the edge of the city undertake the functions of the metropolitan core area and gradually become the main battlefield for the development of new urbanization. This paper takes Yongchuan District of Chongqing as an example, quantitative analysis of the morphological changes of construction land in central urban areas in the past 30 years. It is concluded that the spatial form of the central urban area of Yongchuan District has experienced three periods:single-core constraint filling development, multi-stage point axis expansion development, and multi-group quality improvement enclave development. Then it analyzes the dynamic mechanism of urban morphology evolution from four aspects of productivity, traffic, planning and policy, and discusses the influence of the development of Chongqing metropolitan area on the urban construction of Yongchuan District, in order to provide reference for the construction of county cities in the urban fringe.