Abstract: Effectiveness of interplanting rye grass (Lolium perenne)and milk vetch (Astragalus sinicus L．)in citrus plantation in red earth hilly areas is studied．The results indicate that interplanting has good effectiveness of enhancing efficiency of energy conversion，redueingloss of water and soil，improving soilfertility，yield andfruit quality．However,interplanting would retard the increase of soil temperature in spring which slows down the growth of young trees in spring and summer．To popularize this technique，cultivation and management measures must be strengthened and the relationships between utilization of the forage，conservation of water and soil，fertilizing soil and citrus prodution should be well coordinated to enhance ecological and economic benefits．