The ecological system of the western mountains in Shanxi Province is vulnerable,and soil and water loss has been widely recognized for long time.T he application of converting farm land to forest has efficiently improved ecological environment of the region,profoundly influencing the sustainable development of regional economy of the society.T he comprehensive assessment of converting farm land to forest can provide information regarding the effects of engineering implementation on the society,economy and ecology.Taking Jixian County of Shanxi Province as an example,this study evaluated and analyzed the comprehensive ecological,social,and economic effects of the conversion application between 2000 - 2008.T he results indicate that the comprehensive effect of the conversion in Jixian County was started as negative in 2000,but then increased substantially since the start of 2001.