Plant invasions pose a significant threat to plant community integrity at high latitudes and altitudes, particularly under the backdrop of ongoing climate change and anthropogenic disturbance. However, how plant invasion and increasing invasion intensity reshape community functional traits and multidimensional diversity in high-altitude wetland ecosystems remain poorly understood. Here, we conducted a field survey across 284 quadrats in a subalpine wetland of Shennongjia National Nature Reserve, China. Nine invasive plant species were detected and occurred in 51.06% of all sampled quadrats. We compared functional trait composition between invaded and uninvaded communities and assessed species, functional, and phylogenetic diversity along invasion intensity gradients through inclusion and exclusion models of invasive species. Invaded communities showed 9.1% higher chlorophyll content and 30.7% larger specific leaf area but 26.1% lower leaf density than uninvaded communities. In addition, community-weighted traits and diversity indices showed stronger responses when invasive species were included. With increasing invasion intensity, species diversity and phylogenetic diversity declined, whereas functional richness increased. These results demonstrate that plant invasion simultaneously drives species loss and functional reorganization, reshaping both the functional composition and biodiversity of subalpine wetland communities. Our findings highlight how invasive species restructure plant communities in subalpine wetlands, with important implications for biodiversity conservation in high-altitude ecosystems.