Abstract: Exploring the spatiotemporal changes in crop water requirements and irrigation water requirements under the background of global climate change is of vital importance for adjusting crop planting structures, determining agricultural irrigation quotas, and managing water resources. This study is based on agricultural meteorological data from 13 meteorological stations in the Tibet Autonomous Region from 1979 to 2020 and forecast data from six climate models in CMIP6. It examines the spatiotemporal changes in the main meteorological elements during the growing period of highland barley in the Tibet Autonomous Region during the historical observation period（1979-2020） and the future（2021-2100） under four typical scenarios（SSP126, SSP245, SSP370, and SSP585）. It focuses on the spatiotemporal distribution characteristics of Crop Water Requirement（CWR） and Irrigation Water Requirement（IWR） for highland barley in the near term（2021-2050） and quantifies the impact of the main climate elements on the interannual variation of CWR. The results show:（1） During 1979-2020, the interannual variations of the main meteorological elements during the growing period of highland barley in the Tibet Autonomous Region were characterized by a significant increase in average temperature, a non-significant increase in annual precipitation, and a significant decrease in average wind speed（WND）, relative humidity（RH）, and net radiation（Rn） at the surface. During the historical observation period, the multi-year averages of CWR and IWR were 439.4 mm and 342.7 mm, respectively, both showing a non-significant decreasing trend annually；（2） CWR showed a significant positive correlation with temperature, WND, and Rn, and a significant negative correlation with RH.Among them, the decrease in Rn had the greatest impact on the interannual variation of CWR during the observation period；（3） By the end of this century, the temperature and precipitation during the growing period of highland barley are expected to continue to rise, RH will increase by 2.1% to 8.3%, WND will change by-0.4 m/s to 0.8 m/s, and Rn will decrease by 3.4% to 6.2%. In the near term, CWR is expected to change by-29.3 to 13.6 mm, and IWR will decrease by 23.7 to 113.0 mm. The results of this study can provide a scientific basis and reference for adaptive management of agricultural water resources in the Tibet Autonomous Region under the background of global climate change.