The Lhasa River Basin is a typical arid and semi-arid basin in the Qinghai-Tibet Plateau, where the ecosystem is extremely fragile. It is of great significance to study the spatio-temporal variation of vegetation index (NDVI) in response to the changes of meteorological factors, and to explore the adaptability of vegetation on the Qinghai-Tibet Plateau to the meteorological factors under the background of climate change. Based on the monthly NDVI, precipitation (P), and average temperature (T) time series dataset in the Lhasa River Basin from 1982 to 2017, using Pettitt, Mann-Kendall trend test and Pearson correlation analysis, this paper analyzed the spatio-temporal variation characteristics of growing period NDVI (G-NDVI) and meteorological factors, and identified responses patterns of G-NDVI to climate factors. The results show that the G-NDVI changed abruptly in 1997, and there was a trend shift from increasing to decreasing. The climate of the watershed changed from “wetting-colding” before the abrupt point to “drying-warming” after the abrupt point, and its effect on vegetation growth changed from promoting to inhibiting. There are two zones in the watershed where the responses patterns of G-NDVI to meteorological factors changed before and after the abrupt point. In the western permafrost areas, G-NDVI shows significant correlation with P and T in the second phase after 1997, i.e., emerging the “responding” function on meteorological factors variation. In the southern seasonal frozen zone, after the abrupt point, time lags of G-NDVI to P were elongated, and meanwhile the “responding” of G-NDVI to T has been triggered. The latency of NDVI response to P in the western permafrost region is longer than that in the southern seasonal frozen zone. In the second phase after 1997, the response area of NDVI to meteorological factors increased compared with that before the abrupt point, and the effect of meteorological factors on vegetation growth in the Lhasa River basin was enhanced.