The experiment is conducted with three different forage species which have grown for 4 years on newly-built terrace land in loess hilly region to study the effects on raising the content of soil humus and nutrient by cultivations of Bramus inermis,Astragalus adsurgens and Meliotus albus respectly. The resoults show that the soil humus,nitrogen and phosphorus content can be significantly raised by planting the forage species,the best effect on improving soil fertilities can be obtained by planting Bromus inermis. On the other hand,the content of soil trace element changes with the different utilization of the three forage species. Although the treatment of planting Bromus inermis has the best effect,the yield of millet by planting Bromus inermis previously is relatively low. However, the millet by planting Meliotus albus previously has the highest yield among the three treatments.