In order to analyze the response of plant functional group diversity and species abundance distribution to degradation in the alpine meadow of Gannan, and to explore the formation and maintenance mechanism of the diversity, data were collected by sample plot survey method, and the species abundance model was used for fitting analysis. The results showed that the dominant vegetation species were mainly grass and sedge, and gradually changed to weed functional groups, which played a leading role in the distribution of community diversity. The distribution of species abundance changed with the deterioration degree. The optimal fitting model of non-degraded meadow was VOLKOV, the optimal fitting model of mildly degraded meadow was GEO, and the optimal fitting model of moderately degraded meadow and severely degraded meadow was BRO. The distribution mode of resource allocation changed from random allocation to fixed allocation. The optimal fitting model of grass functional groups is mainly niche model, and the resource allocation mode is dominated by fixed allocation and random allocation. The optimal fitting model of leguminous functional groups is BRO, and the resource allocation mode is mainly fixed allocation. The optimal fitting model of weed functional groups changes from neutral model to niche model, which is basically consistent with the optimal model of all species abundance distribution. In addition, the resource allocation changed from random allocation to fixed allocation, so it can be considered that weed functional groups were the main factors affecting the distribution of community species abundance, but the contribution of grass and leguminous functional groups could not be ignored.