Abstract: A four-year study of sweet orange orchard under contour hedgerow intercropping system has been carried out in sloping farmland with a slope of 15°～38° at Ningnan Station for Sustainable Mountain Development,Chengdu Institution of Biology.Sweet orange trees are planted in the alleys between contour hedgerows of Leucena leucocephala and mulberry trees are planted within the hedgerows.Melon,vegetables and other economic crops are intercropped with orange.Biogas,raising of livestock and sericulture are also introduced to the system.Prunings from the hedgerows have been used as green manure,mulch materials,fodder and raw materials of biogas.The result of the study indicates that more income-generating options are provided to farmers.Economic,social and ecological benefits are apparent.A cost-benefit analysis of the contour hedgerow orange orchard in the initial four years suggests that the cost and benefit ratio is 1∶4.77 while it is 1∶3.27 under using of chemical fertilizers and pesticides.Soil fertility is improved,biodiversity level is enhanced,quality of products is improved of the contour hedgerow orange orchard.Therefore,contour hedgerow intercropping system seems to be a practicable way for development of pollution free agriculture,sustainable use of sloping land,and conservation of environment in mountain areas.