Mountain grassland are an essential component of pasture resources in the Xinjiang Uygur Autonomous Region. However, mountain grassland are highly vulnerable to human-associated disturbance and climate change. The responses of the mountain grassland plant community characteristics and diversity to different grazing managements in Barkol County, Xinjiang, are still unclear. In this study, three different grazing management treatments were set up in 2012 to investigate the response patterns of the plant community characteristics, diversity, and the relationship between the diversity and the aboveground biomass in the mountain grasslands. The three grazing management blocks were M0, M1, and M2, which represented the permanent grazing prohibition, winter grazing, and year-round grazing management, respectively. During the peak growing seasons of 2013, 2017, and 2022, the data regarding the number of species, height, coverage, density, and aboveground plant biomass were collected for further analysis. The results indicated that the different grazing managements had no significant impacts on the importance value of the dominant species, such as Stipa glareosa. However, the importance values of the nondominant species such as Neotrinia splendens and Achnatherum inebrians (Hance) Keng increased under winter and year-round grazing. As grazing intensity increased, plant height, coverage, density, aboveground biomass, and their response ratios declined significantly (P<0.05). There were no significant differences in the Shannon-Wiener diversity, Simpson dominance, and Pielou evenness indices in M0, M1, and M2. In contrast, the Margalef richness index elevated markedly (P<0.05), indicating that grazing provided more survival resources helpful for other species. In the permanent grazing prohibition block, the aboveground biomass was negatively correlated with the Simpson dominance, Shannon-Wiener diversity, and Pielou evenness indices. In the winter grazing block, aboveground biomass was negatively correlated with the Margalef richness index. Overall, the importance value of the dominant species showed no remarkable differences under varying grazing management, and its dominance remained unchanged. Except for the Margalef richness index, the other diversity indices were not significantly influenced by grazing. Winter and year-round grazing enhanced the vital value of unpalatable species, altering the composition of forage, which was not conducive to future animal husbandry development. In summary, as the enclosure time increased, permanent grazing prohibition was beneficial for restoring degraded grasslands, improving community characteristic values, improving grassland productivity, and maintaining community stability to a certain extent. Grazing would affect resource redistribution in the ecosystem, releasing ecological niches for more species, but year-round grazing led to intensified grassland degradation because of overgrazing pressure.