Abstract: Environmental filtering and dispersal limitation are important drivers of beta-diversity in plant communities. This study investigated the relationships between beta-diversity, geographic distance, and environmental distance in rare and endangered plant communities associated with Davidia involucrata and Euptelea pleiosperma along the eastern margin of the Qinghai-Tibet Plateau, China. The aim was to assess the relative contributions of environmental filtering and dispersal limitation on community assembly in these threatened plant assemblages. A total of 21 rare and endangered plant species were recorded across 26 plant communities. Beta-diversity exhibited significant positive correlations with latitude, elevation, soil pH, and soil NH₄ concentration. Furthermore, beta-diversity was significantly positively correlated with both geographic and environmental distances. Multiple regression analysis of distance matrices (MRM) indicated that geographic and environmental distances collectively explained 19.1% of the variation in species composition, while principal coordinates of neighbor matrices (PCNM) analysis indicated that these factors explained 24.5% of the variation. Overall, these results suggest that beta-diversity in rare and endangered plant communities along the eastern margin of the Qinghai-Tibet Plateau is shaped by both environmental filtering and dispersal limitation, with environmental filtering playing a more dominant role in structuring species composition.