Abstract: This paper evaluates the role of medicinal plants in mitigation of soil and water loss in karst mountainous areas. The data are from a test site where 20 kinds of medical plants were cultivated, including Rosa roxburghii Tratt，Fagopyrum dibotrys (D. Don)Hara，Rosa roxburghii Tratt intercropped with Polygonum capitatum Buch.-Ham. ex D. Don，Rosa roxburghii Tratt intercropped with Fallopia multiflora (Thunb.) Harald，and Rosa roxburghii Tratt intercropped with Fagopyrum dibotrys (D. Don) Hara. Regression analysis of monitoring data in raining seasons of 2016 and 2017 shows that the amount of soil erosion has an exponential relationship with plant coverage and the thickness of plant branches and leaves，and a linear relationship with the number of plant roots. In terms of the fuzzy evaluation model, the plants that can contribute to soil and water conservation are Rosa roxburghii Tratt and Bletilla striata (Thunb.) Reichb.f., followed by Aconitum carmichaeli Debx.，Prais polyphylla Smith var. yunnanensis (Franch.) Hand.-Mazz，Codonopisis tangshen Oliv，and Pleione yunnanensis Rolfi. Other plants play a medium role in water and soil conservation. These results would help choose suitable medical plants to cultivate in the areas with varied degrees of soil and water loss.