Abstract: Based on the data of expressway traffic flow of Jiangsu Province, this paper builds the annual expressway traffic flow model, uses the method of social network analysis to explore the centrality and the agglomeration sub group of each county, and combines with the method of geographical detector to analyze the influencing factors from the perspective of the whole of Jiangsu Province, as well as the southern, central, and northern regions of Jiangsu. The results show that:1) On the whole, the spatial distribution of annual total outflow and inflow shows a decreasing trend from the south to the north; the areas with higher outflow rate are located at the junction of southern, central, and northern Jiangsu, the border areas of the whole province and the junction of Zhenjiang City and Changzhou City in southern Jiangsu. 2) The southern Jiangsu, with Suzhou, Nanjing, and Wuxi area as the core, has a strong traffic concentration and radiation effect on the whole province, and the cohesive subgroups show the characteristics of "four groups and eight zones" of the expressway network in Jiangsu Province in general.3) The results of detection factors show that economic level, industrial structure, car ownership, population scale, infrastructure, and purchasing power of residents all have a significant influence on the expressway flow in the province, and the explanatory power of factors are different in various regions.

Key words: expressway traffic flow, spatial network differentiation, social network analysis, geographical detector, Jiangsu Province