Drylands cover about 41% of the Earth's land area， support more than 38% of the world's population， and are home to most of the world's developing and poor populations. Drylands are one of the most sensitive areas to the impacts and responses to global climate change， and it is essential to study the changes in their climate， hydrology and ecological environment. There have been many studies in this area in recent decades， but the conclusions are fragmented and there are many inconsistencies. Based on the analysis of domestic and international literature， this paper summarizes and composes the changes in climate， hydrology， area and type of drylands under climate change and the impacts of these changes on ecosystems. The main results of the combing are as follows. CO2 emissions from dryland are only about 30% of those from humid areas， but the warming rate is 20%~40% higher than that of humid areas. In the past half century， the dryland area has increased by about 2.61×106 km2， and by the end of this century， the global dryland area will continue to expand by about 5.8×106 km2， which will occupy more than half of the total land area. Under the background of global warming， the water resources system based on precipitation and snow melt recharge in drylands will be more fragile， and hydrological elements such as ice and snow and water resources composition will change， hydrological fluctuations will increase， and water resources uncertainty will intensify. Along with the expansion of dryland area and the increase of aridity， the shortage of water resources， shrinkage of water bodies， degradation of ecosystems and desertification in dryland areas will also intensify， and the future socio-economic development and ecological security of dryland areas will face more severe challenges. Some comprehensive conclusions condensed from these inductive combs are of reference significance for governmental decision making and for proposing credible and clear scientific understanding in the future.

Keywords： Climate change ; Dryland ; Water resources ; Desertification ; Ecological crisis