To explore the sensibility of the response of plant community structure to external disturbances under different degradation conditions in the Northwestern Yunnan Province (NWYP), we conducted a mowing experiment at three degradation gradients (i.e., S1:severe degradation; S2:moderate degradation; S3:slight degradation) in an alpine meadow in Shangri-La from 2018 to 2020. The effects of mowing on community structure indicators, including species richness, community similarity, community complexity and keystone species were analyzed. The results showed that (1) after mowing, the species richness of S1 increased significantly (P<0.05), while the species richness of S2 and S3 did not change significantly (P>0.05). (2) Mowing caused a greater change in community similarity in S1 than in S2 and S3. (3) The network connectivity of plant community decreased firstly and then increased after mowing in all degradation levels. Moreover, the change range of community complexity in S1 was higher than in S2 and S3. (4) The keystone species of plant communities changed in 2018, 2019 and 2020. In S1, the keystone species varied between Leguminsae and Rosaceae. In S2, the keystone species varied between Gramineae and Compositae. In S3, the keystone species varied among Rosaceae, Compositae and Gramineae. The study suggests that the sensitivity of the response of species richness, community composition and complexity of plant community to external disturbance might increase with meadow degradation levels, while the shifting of the keystone species would be complex in NWYP.