Abstract: Vegetation phenological changes in the Tibetan Plateau play an important role of global climate change. However, the study on the effects of climate change on phenology in this region is still insufficient. Therefore, in this study, remote sensing data MODIS (MOD13A2) NDVI was used as the data source to invert vegetation phenological changes in Tibetan Plateau grassland from 2000 to 2023. The results show that: ①The variation of precipitation and temperature over the Tibetan Plateau has obvious zonal regularity, with precipitation lower in the west and higher in the east; The overall temperature shows a trend of low in the west and high in the east. ②The 111～192 days are the main time range of SOS occurrence, accounting for 61.21% of the total area. ③In February, the positive correlation between air temperature and SOS is the highest, 55.96%. The main conclusions are as follows: ①The SOS of the Tibetan Plateau shows an overall advance trend during 2000—2023, while the EOS shows a delayed trend. ②SOS is negatively correlated with precipitation in February in the early growing season, while EOS is positively correlated with precipitation in August in the late growing season.

Key words: Tibetan Plateau, phenomenon change, annual mean temperature, annual precipitation, lag effect