Based on the long time series vegetation, precipitation, temperature and drought data sets of the Yarlung Zangbo River Basin from 1981 to 2015, the non-parametric statistical methods Sen's slope and Mann-Kendall trend test were used to identify the spatio-temporal change characteristics of each element. Pearson correlation analysis and geostatistical method were used to analyze the time lag effect of vegetation cover response to climate change, and the impact mechanism of climate change on vegetation dynamics was discussed. The results show that the normalized difference vegetation index (NDVI) is generally increasing in spatial distribution from upstream to downstream, and the vegetation in some regions of the middle reaches has improved, while there is some degradation in the lower reaches. The upper reaches of the basin are mainly affected by temperature and become arid, while the middle reaches and lower reaches tend to become warm and humid due to precipitation. NDVI in the upper and middle reaches of the basin has a significant positive correlation with precipitation and drought, and the correlation is highest mainly when it lags behind 1 month. NDVI in the middle reaches and southeast of the lower reaches has a significant negative correlation with temperature, and it is distributed in areas that lag behind 0 to 3 months.