Abstract:  City is the center of a region and the engine for regional economic and cultural development, playing a radiation and leading role in the surrounding areas. Whether the city size structure is reasonable or not is crucial for the reasonable allocation of urban resources. With cities at or above Countylevel in Jiangxi Province as samples, the population sizes of cities were investigated and analyzed with urban primacy index, ranksize rule, etc. The results showed that the city size structure of Jiangxi Province was typical urban primacy index distribution, with characteristics of lacking large and super cities, less mediumsize cities, more smallsize cities, small city size overall, and significant differences between city size in northern and southern areas. The cities of Jiangxi were divided into three urban agglomeration, northern, central, and southern one in the spatial distribution. It was indicated that the urban spatial distribution of Jiangxi was with three characteristics: urban agglomeration, obvious difference between north and south, and the direction role of traffic route. Finally, we briefly put forward some suggestions based on the above results.