[Objective] The ecological cleanliness in the small watershed of the typical ecological clean basin in South Sichuan Province was evaluated, in order to effectively guide the formulation of the implementation plan for the construction of ecological clean and small watershed in mountainous areas, and to provide scientific theory and data support for the construction of ecological clean small watershed in similar areas and the evaluation of its effect. [Methods] Based on the principles of representativeness, operability and applicability, according to the natural, social and economic characteristics of the Qingxigu small watershed, a comprehensive evaluation index system for eco-cleanliness evaluation in Qingxigu watershed was established by fuzzy mathematics method and analytic hierarchy process. [Results] The comprehensive evaluation index system of ecological cleanliness in Qingxigu watershed included 3 subsystems: ecological region, production region and living region, and 24 evaluation indices were chosen. The weight of the ecological index of watershed regulation of water system and soil conservation measurements was 0.247, the weight of ecological agriculture development was 0.373, the weight of renovating environment of human settlements was 0.380, and the total value of the ecological clean watershed was 0.772, reaching the ‘clean’ level. It indicated that the Qingxigu small watershed was in a healthy, coordinate and stable development. [Conclusion] The construction of eco-clean small watershed could improve the local agricultural condition, adjust production structure, control the non-point pollution, supply the pure and clean water resource and accelerate the sustainable development of the watershed.