Xizang Plateau is one of the regions with extremely concentrated ecological system types and biodiversity in China's alpine ecosystem. The high-altitude typical grasslands and alpine meadows are the main grassland ecosystem types. Due to its weak system vitality, organization and resilience, it is strongly vulnerable to the impact of global climate change. For many years, the studies on the distribution of plant communities and their changes and responses to various environmental factors in the grassland ecosystem of Xizang Plateau have been focused on site scale or transect scale, but the results are still uncertain. We selected 14 sample plots of alpine grassland areas along different wettability gradients in Xizang region. Through investigation of vegetation community and analysis of soil physical and chemical properties, we explored the response characteristics of spatial pattern of herbaceous vegetation community to climate factors and its main driving factors. The results provided basic scientific data support for the protection and sustainable utilization of natural grassland on Xizang Plateau. The results show that: (1) the research region can be divided into arid zone, semi-arid zone, semi-humid zone, and humid zone. The aridity degree in the northern part was gradually decreasing from 1971 to 2021, while that in the southern part was gradually increasing during 1991-2010. The humidity index of the whole study area was decreasing. (2) The investigation of plant community found that the changes of different plant functional groups were different. The aboveground biomass of Cyperaceae increased with the increasing humidity, while that of Miscellaneous grass showed a unimodal trend, the other community had no obvious regularity. The Shannon-Wiener diversity index, Simpson index, richness index, and evenness index of plant community in semi-humid zones with higher humidity were higher than those in other humidity zones. (3) The analysis of soil physical and chemical properties found that the soil moisture content, total nitrogen, nitrate nitrogen, ammonium nitrogen, and available phosphorus content in high-humidity areas were the highest. Based on the correlation and principal component analysis of various environmental factors and plant community characteristics, the structural equation model was established. The factors that directly affected the changes of plant community characteristics in alpine grasslands on Xizang Plateau were wettability, soil moisture content, and soil pH, showing the significantly negative effects (P<0.05). However, wettability had significantly positive effect on soil water content and soil total nutrient (P<0.05), which further affected the distribution, diversity and aboveground biomass of different plant functional groups in alpine grasslands on Xizang Plateau.