The returning farmland to fo rest project has brought important effects on the succession of regional agricultural eco-economic system. By analyzing the implementation effects of the project in Mizhi County of high population density over the past 10 years, it is found that vegetation is restored and forest coverage is increased by 13. 85%. Soil and water loss is controlled effectively and the degree of soil and water loss control is enhanced by 12.73% . Farmers income has been raised, their lifestyle and ideas have been changed notably, and regional industrial structure has been optimized. It also proves that ecology can be coordinated with economy in the development of the loess hilly area.