[Objective] The succession of vegetation community in the process of grassland shrub encroachment will affect the soil organic carbon pool, and the active components of soil organic carbon ( SOC ) can quickly reflect the change of soil organic carbon pool. By exploring the effect of shrub encroachment on the active components of SOC in alpine meadow, it is expected to provide data support for the study of soil organic carbon pool change and carbon sequestration in grassland of Qinghai-Tibet Plateau under the background of global climate change. [Methods] Taking the Caragana erinacea shrub meadow in the Qinghai-Tibet Plateau as the research object, the changes of soil physical and chemical properties, carbon cycle enzyme activities and SOC active components in 0-10 cm, 10-20 cm and 20-40 cm at different shrub encroachment stages ( non-shrub, moderate-shrub and severe-shrub meadow ) were analyzed. [Results] ① The soil water content ( SWC ) in the 0-20 cm soil layer decreased significantly, and the SOC content in each soil layer was the highest in the heavy shrub meadow, and the soil pH increased significantly in the moderate shrub meadow. ② The soil amylase activity ( SAA ) of moderate shrub meadow was significantly lower than that of non-shrub meadow, and the soil sucrase activity ( SSA ) of 10-40 cm soil layer was also significantly lower. SSA was significantly stronger than that of non-shrub meadow in the severe shrub stage. ③Compared with non-shrub meadow, the content of readily oxidizable organic carbon ( ROOC ) in 0-10 cm, 10-20 cm and 20-40 cm of moderate shrub meadow decreased by 16.79 %, 21.73 % and 31.11 %, respectively, and the content of dissolved organic carbon ( DOC ) and microbial biomass carbon ( MBC ) in 0-10 cm soil also decreased significantly. The contents of particulate organic carbon ( POC ) and ROOC in 0-10 cm soil increased significantly by 24.37 % and 29.54 %, respectively. The contents of MBC and DOC in 10-20 cm soil increased significantly by 12.96 % and 10.38 %, respectively. The contents of MBC and DOC in 20-40 cm soil increased significantly by 57.62 % and 22.10 %, respectively. ④ Soil organic carbon active components were significantly positively correlated with TN, SWC, SOC and carbon cycle enzyme activity, and ROOC was significantly negatively correlated with pH. [Conclusion] The content of soil organic carbon active components in the early stage of Caragana erinacea shrub encroachment in the study area decreased, while the soil organic carbon and its active components were accumulated in the later stage of shrub encroachment, which may have a positive effect on the accumulation of soil organic carbon and the improvement of soil quality in this area.