Huaihai economic zone, composed of northern Jiangsu, northern Anhui, eastern Henan and southern Shandong, has been underdeveloped for a long time. Now its development upgrades to a national strategy. Construction of the northern part will promote a co-integrated development of the whole zone. This paper uses gravity model to study the spatial structure of urban group of Huaihai economic zone with its results showing a urban comprehensive quality range from 218.16 to 1 062.58. Xuzhou city has the largest gravity within the zone, but has larger fault point average value with Jiangsu, Shandong and Henan, while smaller with Anhui, indicating a weak radiation of Xuzhou to Anhui's cities. Cities in Huaihai economic zone develop at uneven rates with XuHou as the center but with limited attraction and variable economic attractive force to other cities. Economic exchange and communication in the economic zone need to be improved, not only on Xuzhou's radiation, but also on Linyi and Huaian's diffusion as sub-centers, which boosts the integration of regional economy.