The response of plant to drought stress reveals the distinct expression of functional traits. With the global climate change, the precipitation pattern of the Qinghai-Tibet Plateau has been altered. It is of great significance to explore the response mechanism of functional traits and functional diversity of alpine meadow communities in drought events, which would enable an in-depth understanding of the adaptation of climate change in alpine meadows. In this study, we conducted manipulative drought experiments with early growing season drought (ED), middle growing season drought (MD), and non-growing season drought (ND). We observed the functional traits of community species and analyzed the response mechanism of functional diversity of alpine meadow communities to drought in different growing seasons. The results showed that:(1) there were different responses of leaf functional traits to drought, which showed that the leaves were small, thick and long-lived, the assimilation rate was reduced, and it was aggravated by nitrogen restriction. (2) The effect of drought in the early growing season on the functional traits of alpine meadow communities was the strongest, followed by the middle of the growing season, and the weakest effect in the non-growing season. (3) Drought in the growing season significantly changed the functional diversity of the community. The functional divergence (FDiv) and functional dispersion (FDis) were significantly reduced in ED (P<0.05), while the Rao's quadratic entropy (RaoQ) was significantly increased (P<0.05), and the functional evenness (FEve) was significantly reduced in MD (P<0.05). (4) Correlation analysis showed a link between community functional traits and functional diversity's response to drought. The study found that the functional traits and community functional diversity of alpine meadows had differential responses to drought in the early and middle growing seasons. This indicates that alpine meadow plant communities may take different survival strategies in response to drought in different periods, that is, the community adopts drought tolerance strategies for drought in the early growing season and drought avoidance strategies for drought in middle growing season. In this study, we investigated the response mechanism of plant community functional diversity to drought stress in different growth periods of alpine meadow. We provided a scientific basis for predicting the effect of seasonal drought events in the future on plant functional traits, community weighted means (CWM) and functional diversity in the alpine meadow on the Qinghai-Tibet Plateau.