As a fundamental measure of eco-environmental restoration, the process of returning slope farmland to woodland and grassland is being conducted in the reservoir area of Three Gorges Dam gradually. However, de-farming of slope farmland will reduce the amount of farmland in the de-farming area, this is especially true in areas with concentrated slope farmland. The people who de-farm their farmland can obtain enough farmland again in two main ways: some of them can gain enough farmland by adjustment of farmland with those in the same village, the others can not gain enough in local area and have to emigrate to other places. The latter can be called environment emigrants or ecology emigrants. In the research, we set up a de-farming stress index model and an environmental emigration model using GIS based on GRID data structure, and simulate the latent amount of environmental emigration caused by dc-farming of slope farmland in the reservoir area. The simulation indicates that the latent emigration amount caused by de-farming is quite large. When the de-farming stress index reaches 40%, the amount is as large as 890 000, which is equivalent to the allocated amount of the emigtants around the reservoir caused by the submergence of the Three Gorges reservoir area. So it should be considered as a big problem in the eco-environmental resteration in this area. To resolve the emigration stress, some suggestions are put up in this research: Firstly, the emigration plan should be included in the de-farming plan. For the successes of the experience, some financial support policies are attempted. But the effects are limited. As the dc-farming experiences are conducted in wider regions, the financial support will become a heavy burden. So emigration is the fundamental countermeasures to reduce population stress in slope farmland. Secondly, besides the Three Gorges reservoir area, other provinces especially those located in the lower reaches of Yangtze river should adapt part of the environment emigration . Those provinces such as Hubei, Hunan, Jiangxi benefit from the ecological effects of the de-farming project.