Farmland ecosystems are fundamental to human survival, and the response and feedback of farmland ecosystem services to the impacts of major projects are of vital importance for guiding regional social and economic development. Based on agricultural production data of the Three Gorges Reservoir Area (TGRA) before and after impoundment (2002, 2011), the Ecosystem Service Value (ESV) of farmland in the TGRA was estimated; changes in its characteristics and environmental pressures were also discussed. The results show that (1) after impoundment, each ESV of farmland increased, and the Total Value increased by 16.81%; the values of product supply, leisure tourism and gas regulation dominated the increase of the Total Value; compared with product supplying and life ensuring, the value of ecological regulating showed a relatively small increase. (2) The change in the Total Value was the result of natural and human activities, including the Three Gorges Project; the increase in Regularly Cultivated Land, planting structure adjustment, increased use intensity of chemical fertilizer and pesticide, development of leisure tourism, and increased scientific research input were the major reasons for the increase of the Total Value. For some counties, especially those with decrease in Regularly Cultivated Land, planting structure adjustment and the increased use intensity of chemical fertilizer and pesticide might be the main reasons for the increased farmland ESV. After being normalized to the consolidated value of year 1990, the inundation of cultivated land decreased the farmland ESV by 424 million yuan per year, among which the value of product supply was 137 million yuan peryear. (3) The increased use intensity of chemical fertilizer and pesticide, and the decreased contribution of chemical fertilizer to crop yield were the environmental pressures imposed by maintaining and promoting the product supply of the farmland ecosystem in the TGRA. Moreover, the farmland ESV was not only influenced by the above-mentioned environmental pressures, but also by the increase in population, the decrease in agricultural population, the decrease in land resources, and the inundation of high-quality cultivated land.