This paper designs a theoretical model of excess per-capita income growth and brings forward such indices as excess per-capita income, per-capita base consumption and decreasing factor as well as the corresponding measurement methods. It studies from a brand new aspect the disparity between the economic growth in urban sector and rural sector of China in the past 30 years after the reform and opening-up, together with the disparity between the effects of such growth on consumption. The research results show that: At present the problem of the duality of urban and rural sector of China is still serious; the impaired amount of economic growth in urban sector is larger than that in rural sector while the impairing strength in rural sector is higher than that in urban sector; and it is vital to increase the excess per-capita investment in rural sector in order to effectively strengthen consumption related policies. Therefore, promoting urbanization but reasonably controlling the urbanization progress while strengthening the infrastructure construction in rural areas would be the efficient approach to reduce the impairing strength over the economic growth, to build up consumption market, to improve the duality of economy and to realize sustainable development.