To analyze the response of NDVI to climate change and its time-lag effect in multi-time scales,synthetic data NDVI detected by NOAA-AVHRR,monthly observed data of precipitation and temperature from 1989 to 2008 were used in this paper. On this bases,we built NDVI prediction models to forecast trends of NDVI under different emission scenarios in the future. Results showed that: (1) NDVI high value areas existed in southeastern and eastern Three-Rivers-Source Region,and gradually become lower to West-north direction. Months from April to August were growing seasons for vegetation,when NDVI reached maximum in August. (2) Variations of NDVI in spring,summer,autumn displayed an obvious positive phase with temperature and precipitation excluding the summer precipitation; correlation features in spring and autumn were especially remarkable; the response of NDVI to temperature was higher than that to precipitation. Time-leg effect of NDVI in the current month showed most significant correlation feature with the last month's temperature and precipitation. (3) Under the background of Three-Rivers-Source Region's climate warming and slightly increasing precipitation from 2006 and 2050,average NDVI increased significantly,slower in the first decade,and faster in the next three decades with large growth rate. Distribution of NDVI was essentially constant in spatial,and increasing centers with highintensity and large-range under RCP8. 5 scenario were much prominent than that under RCP4. 5 scenario. Years of 20162035 were rapid growth phase with increasing center of Lancangjiang source region under RCP4. 5 scenario. Periods of 20162025 and 20362045 were rapid increasing time with high variability center of yangtze river source region under RCP8. 5 scenario. Location of high variability center in coming multi-decades shifted from north to south in Three-Rivers-Source Region under both scenarios.