Under the influence of the "space of flows" theory, city network with the emphasis on element connectivity and spatial relevancy has become the core perspective to indicate the regional spatial interaction. This means that researchers focus more on spatial structures of city networks, which can provide scientific basis for the policy making on regional development. Based on the average daily variation expressway traffic flow data in 2014, this article depicts the macro-patterns of city networks and its hierarchical structures, and then uses the community detection algorithm to segment the city networks and mining its potential spatial correlation structures. The results show that: (1) The characteristics of macro-patterns of city networks are dispersive, which are similar to the "gold corner, silver edge, grass belly" in Go Game, and this means that there are several sub-network systems developed in Jiangsu province. (2) The city nodes and linkage axes have presented the obvious hierarchical structures. On the one hand, the importance of the city ranks has a spatial coupling with their socioeconomic attributes and geographical locations to certain extent; On the other hand, the hierarchical characteristics of the linkage axes have obvious spatial interaction with the geographical distance. (3) Using the community detection algorithm to mining the city network in Jiangsu, six "city communities" with spatial connection and clear boundaries are identified. The communities include the Suzhou-Wuxi-Changzhou community, Nanjing-Zhenjiang-Yangzhou-Taizhou community, Nantong-Yancheng community, Lianyungang community, Suqian-Huai'an community and Xuzhou community. The spatial metaphors of the communities can be concluded in the five aspects. Firstly, trans-prefectural linkages can be formed through spatial integrated effects of metropolis regions. Secondly, cities are located in the marginal neighborhood areas in different communities and have a close connectivity, which enable themselves to be absorbed into the neighboring community due to the distance attenuation effect. Thirdly, some communities have the same boundaries with the prefecture level administrative units, which reveals that significant administrative region economy still exists in contemporary Jiangsu province. Fourthly, several cities located in the marginal areas of the prefectures and captured by the powerful center cities in the neighboring prefectures would lead themselves to be absorbed into the communities of the neighboring prefectures. Fifthly, the couple gateway cities serve as the linkages in different prefectures because of their strong strength with the surrounding areas, which would be exchanged by each other. According to the spatial interaction in paired communities, there are seven spatial interactive structures that can be divided, i.e., dual-nuclei structure inter-cross connection with polycentric structure, dual-nuclei structure inter-cross connection with monocentric structure, monocentric structure inter-cross connection with polycentric structure, monocentric structure inter-cross connection with monocentric structure, dual-nuclei structure inter-cross connection with low-level equilibration structure, monocentric structure inter-cross connection with low-level equilibration structure and polycentric structure inter-cross connection with low-level equilibration structure.