As to a theoretical model, the analysis of external phenomena and mechanism is not far enough. The essential intention is that the model of theory could be put into practical analysis of spatial structure of a region. Jiangsu locates to the border district along the coast and along the Yangtze River, so it becomes a most perfect region in which we can use the model of dual-nuclei structure to instruct evolution of city spatial structures. The application of the model of dual-nuclei structure before and after the adjustment of regional administration of the Huaian city is a typical case. It was emphasis of the spatial layout and development in Huaian city in the past to construct the Guanhe economic corridor and to establish the city of Guanhe. At that time, based on the development condition of Huaian city, the productive forces layouts of it provided some advices on establishing the industrial axis that is composed of Huanan city and the port of Guanhe, relying on Huanan municipalities and taking the comprehensive development of the Guanhe port as the development emphasis. The Guanhe city must be established. This idea conforms to the model of dual-nuclei structure that is composed of a regional central city and a port city. Therefore, the adjustment of regional administration makes the spatial layout strategy falling into a tight corner. The initial scheme of space layout in Huanan would not be carried out further. Based on the spatial combination theory between the cities, we think that Lianyungang city should be the gate port city of Huaian which is the central city of region. The improvement of communication condition recently provides the premise condition to form the model of dual-nuclei structure that is composed of Huaian and Lianyungang city.