Regular assessment of conservation effectiveness plays a crucial role in conservation decision-making and improvement of protected-area management. Landscape dynamics can directly indicate the conservation effectiveness of protected areas. However, there is still limited research on assessing the effectiveness of landscape conservation of regional protected-area networks by applying a multi-index evaluation approach. With 102 national and provincial-level nature reserves in Southwest China as the study objects, this paper used the entropy weight-TOPSIS method to implement a comprehensive assessment on these reserves' landscape conservation effectiveness based on indices of four groups including landscape ecological condition, natural habitat pattern, connectivity, and human disturbance. We aim to assess the conservation effectiveness of nature reserves over a long-time scale from 1990 to 2015, and also to investigate the relationship between conservation effectiveness and two attributes of nature reserves, i.e. their types and administrative levels. The results showed that:(1) during the assessing period from 1990-2000 to 2010-2015, the number of nature reserves with improved conservation effectiveness accounted for 77.5%, but the number of nature reserves that had a lower value than the average of the comprehensive evaluation index of conservation effectiveness continued to increase. It indicated that on the one hand, the overall conservation effectiveness was improved; on the other hand, the landscape conservation effectiveness of some nature reserves was relatively low. (2) The landscape conservation effectiveness of nature reserves exhibited a clear heterogeneous spatial pattern. The nature reserves with significantly increased conservation effectiveness were mainly distributed in Sichuan, Xizang, Yunnan and Guangxi, whereas the nature reserves with significantly decreased conservation effectiveness were mostly located in Guizhou, Guangxi and the bordered areas between them. (3) The landscape conservation effectiveness varied with the types and administrative levels of nature reserves. In terms of types, the forest-ecosystem nature reserves had the highest overall effectiveness, followed by inland-wetland, wild-animal and wild-plant nature reserves, but wild-animal reserves had the highest degree of improvement in conservation effectiveness, followed by inland-wetland, forest-ecosystem, and wild-plant nature reserves. In terms of administrative levels, the national nature reserves had higher effectiveness than provincial nature reserves. In general, the nature-reserve system in Southwest China achieved significant landscape conservation efficiency for natural habitats, but some nature reserves (e.g. Maolan, Mayanghe, and Chishui Alsophila Nature Reserves) showed obvious decline in landscape conservation effectiveness, which needed more attention. This research can provide scientific support for the improvement of conservation effectiveness and the spatial optimization of protected-area systems in regional scale.