Legume crops and pastures canfix large quantities of nitrogen(N₂) from the air if they are well pelletized and inoculated by the most effective strain of rhizobium bacteria.The principle and benefit of nitrogen fixation of legumes,and some other practical problems have been discussed.It is considered that the legumes inoculant technology is the key to control and improve degenerated grassland, and can promote the sustainable development of agricul-ture powerfully.