The construction of the town-group of Yiyang, Yuanjiang and Taojiang is an important measure to raise the regional competition, to make up the new economic growth in the northern Hunan area. Taking the SPSS software to survey the strength of economic development and linking the space gravitation interaction model to estimate the economic growth between the county towns and the Yiyang centre city. The order of the basic situation is Yiyang, Yuangjiang and Taojiang Towns.As the quantitative analysis the result shows that Yiyang City is the absolute economic center, which exists the economic gap between Yuangjiang and Taojiang. Of course Yiyang is larger and the leading role in the economic radiation. It is of the highest power of gravity. Taojiang County is near to Yiyang. The gravitational strength and degree of order membership is the second row. Yuangjiang City is the third. By analysis of the economic position of the urban agglomeration it can provide economic and rational development of the town order of Yiyang, Yuangjiang and Taojiang.