Abstract: Hubei and Hunan Provinces were sparsely populated at the beginning of the Qing Dynasty, however, most of southern Hunan had occurred because of the land development all overpopulation problem.This directly affected the local traditional agricultural economy and caused hardship and impinged upon the people's food supply.Southern Hunan was the first region to introduce maize, sweet potatoes and other high-yield upland grain crops. In Hubei and Hunan Provinces,such man-land relationships had objectively stimulated diversified economic development in the region. The two crops were widely planted after the middle of the Qing Dynasty, the hardship of food scarcity in southern Hunan was effectively alleviated. Southern Hunan also experienced rapid population growth.The introduction of new crops and the demographic expansion were powerful factors promoting the further development of the local community's economy. What needs to be pointed out is that population pressure and labor substitution forced economic development,but there was no general improvement in the living standards of the people. These economic developments had the obvious historical limitations．