Because vegetation rehabilitation in western China centered on returning farmland to forest or grassland is a complicated eco-economic system engineering,we must establish a long-term steady policy and law insurance system while establishing a long-term steady economic compensation mechanism,which should be based on biological zone of vegetation determined by climatic elements such as water and heat,driven by market economic mechanism of regional complementation under national control.To this end,we discussed several scientific issues which include the geographical pattern of natural vegetation in western China,moderate returning size and rehabilitation technology after returning,environmental service function output of vegetation restoration engineering,ecological industry and economic compensation mechanism,and the pro-tection and improvement of natural vegetation as well.At the same time,we pointed out some er-roneous understandings and ill tendencies in the pilot project of returning farmland to forest or grassland.