Owing to the various situation, the conversion of farmland(back to forest or grassland) in foreign countries has various objectives, such as alleviating social contradiction, eliminating grain overstock, conserving biodiversity, reconstructing landscape, mitigating greenhouse effect, etc. Proceeding from analysis of the farmland's conversion abroad, we can make a conclusion that economic strength is the basis of this kind of farmland's conversion, the surplus of grain is the pledge and the shift of labor to towns or cities is the precondition. Furthermore, the success of the farmland's conversion benefits from the changes of revenue policies to a great extend. To put the Farmland's Conversion Project into effect in China, taking the experience of other countries and considering of China's specific situation, this research proposes two advises: on the one hand, the economic construction and grain production must be strengthened; on the other hand, the living of the farmers who convert their own cultivated land back to forest or grassland should be well arranged. The government may carry out a series of preferential policies about revenue and credit etc. to make those farmers live better.