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Through the construction of a corresponding index system, the competitiveness of cities in the middle reaches of the Yangtze River in 2015 was measured using principal component analysis, and based on their road traffic layers, the accessibility of cities was measured using GIS grid cost distance spatial analysis technology. Then, the entire spatial field strength was simulated using the field strength model, and the hinterland of the cities was extracted according to the maximum principle. This was done to effectively define the spatial scope of the urban agglomeration in the middle reaches of the Yangtze River. The spatial distribution of urban competitiveness in the middle reaches of the Yangtze River was found to be quite different, and the difference between the maximum and minimum values was 5.84, which is related to the administrative level. In terms of accessibility, the 1-h circle mainly concentrates in the vicinity of the central part of the city, and the 3-h circle and above mainly distributes in the periphery far from the provincial capital city as well as in the Yue-Jiu-Xian provincial boundary area. There is a lack of unified planning and coordination regarding inter-city traffic development in the middle reaches of the Yangtze River, and internal traffic links are relatively weak. Regarding spatial field energy, the high field energy area was concentrated in the central city and its surrounding areas, while the low field energy area was distributed in the marginal and peripheral areas with poor traffic accessibility, particularly in the provincial border areas. The spatial distribution of field strength was in good agreement with the distribution of urban competitiveness and traffic accessibility; However, the degree of inter-provincially coordinated development was low. From the perspective of urban hinterlands, the hinterlands of most cities in Hubei Province are smaller, the hinterland of Jiangxi Province is relatively vast, the hinterland of Hunan City is medium sized, and the hinterland of the three provincial capitals is much larger than those of other cities, which means that the urban agglomeration in the middle reaches of the Yangtze River has formed a complex polar nuclear development pattern with the provincial capital cities as the multi-center However, the degree of internal integration is weak. From the overlapping results of the hinterland and administrative scope, the consistency between the urban hinterland and the municipal administrative scope is poor. Cities with an expansion rate that is greater than 1.1 were mainly Wuhan, Changsha, Nanchang, Yichang, Changde, Pingxiang, Xinyu, Jingdezhen, and Yingtan. Cities with an expansion rate above 0.9 and less than 1.1 mainly included Hengyang, Loudi, and Yueyang. In Xiangyang, Tianmen, and Qianjiang, the expansion rate of other cities was less than 0.9. In addition, the proportion of extraterritorial hinterland of the three major provincial capitals was found to be much higher than that of other cities. The proportion of extraterritorial hinterland of Jiujiang, Yueyang, Yichang, Changde, Xinyu, and Jingdezhen was also higher. Generally, urban agglomeration in the middle reaches of the Yangtze River has stayed consistent at the stage of integration within the sub-circle and has not yet realized integration of the three circles or highly integrated development. This study attempted to identify the spatial range of urban agglomerations by using GIS quantitative analysis technology, and we provide reference for optimization and integration of the urban spatial structure of urban agglomerations in the middle reaches of the Yangtze River.
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