Predicting the impact of overgrazing on soil properties, and thus on plant succession, in the Qinghai-Tibet Plateau (QTP) is one of the primary technical bottlenecks in alpine meadow conservation. Four degradation intensities, namely D1: light degradation, D2: moderate degradation, D3: high degradation, and a non-degraded site as the control (CK), were identified. The soil properties and plant community data were analyzed. With the increase in degradation intensity, the soil pH, conductivity (EC), and bulk density (BD) values significantly increased, while the soil water content, total carbon, total nitrogen, and C/N ratio significantly decreased (p < 0.05). Plant aboveground biomass and Shannon diversity significantly decreased with the increase in degradation intensity (p < 0.05). The dominant species changed from Poa pratensis (CK) to Potentilla multifida (D1), to Iris lactea (D2), and finally to Achnatherum splendens (D3). Overgrazing can lead to changes in soil properties, and changes in soil pH and BD are the primary factors that control the changes in plant community structure and composition with grassland degradation. Soil degradation is conducive to the growth of individual species such as A. splendens, which are associated with a reduction in plant diversity in an alpine meadow of the northeastern QTP. Future research should pay more attention to the key species and soil properties in degraded grasslands.