The important step for boosting coordinative development of new-style industrialization, informationalization, urbanization and agricultural modernization is to systematically propel the citizenization of the farmers who left the countryside and by letting the famers gradually quit their contracted land. According to Logistic Model and the survey data on 1086 households who left the countryside in Henan, Hunan, Sichuan and Chongqing, the analysis shows that two big engines for the farmers to quit their contracted land are to seek maximum economic compensation and to pursue higher living quality, that the willingness and behaviors for the farmers to quit their contracted land are restricted by direct cost and indirect cost produced in the process of the land withdrawal, that the increase of non-agricultural income and social security level of the farmers can boost the land withdrawal, and that the prospect for working stability and living condition improvement after the land quitting is the main factor for the farmers to consider the land quitting. Thus, China should not only get rid of “urban and rural dual system barrier” but also remove “urban and rural dual economic barrier”, must consider the willingness of the farmers to quit their contracted land in household register system reform and rural land system reform, should sufficiently protect the rights of the farmers who quit their contracted land, should practically reduce the risk for the land quitting, should consolidate low-rent housing construction and enhance apartment-buying subsidy to decrease the cost for the farmer citizenization, should boost the employment training for the farmers, should promote the establishment of social security system and should constantly improve the ability of the farmers, besides, should build the associated mechanism for traditional farmers’ land withdrawal and for professional farmers’ acceptance of the quitted land, in order to realize agricultural modernization.