Yunnan province is rich in biodiversity and is critical for providing ecosystem services. Human disturbances and climate change in recent decades have put the ecosystem under stress, making it urgent to study biodiversity and stability of this region. Here, sediment records covering 1820s-2006 were collected from Lake Yangzong and were used to explore the patterns of diversity and stability and their relationship. Changes in lake nutrient, chironomid diversity (species richness), evenness (Invsimpson), similarity (Jaccard) and stability (ar1) were reconstructed based on nutrient indicators (total organic carbon (TOC) content, total nitrogen (TN) content and TOC/TN) and chironomid assemblages. Principal components analysis of chironomid community data was used for critical point detection. We found that TOC and TN contents increased, and abrupt changes in the chironomid community occurred since 1990. Meanwhile, community diversity, evenness and similarity all showed a rising trend. Clear increases in diversity from the 1950s, evenness from the early 1990s, and similarity and instability from 1970s indicate higher diversity and evenness of chironomid communities, corresponding well with the rising in TOC content. The increasing in TOC/TN ratio had a positive correlation with species richness, evenness and similarity, respectively, however, a negative correlation was obtained with stability. The significant negative correlation between chironomid species richness and stability in Lake Yangzong suggested that the species richness depleted its stability.