Water resource is an essential part of the ecosystem in the extremely arid northwestern China.Previous studies revealed a dry-to-wet climate change since the late 1980s in this region,which suggested a relief from the drought condition.However,the analysis in this study using the updated data shows that the arid situation has continued and even intensified in the recent decade.This is reflected by the fact that the low-level air relative humidity and deep soil relative humidity has decreased in the past decade.The examination of the standardized precipitation evapotranspiration index(SPEI)and self-calibrating Palmer drought severity index(sc-PDSI)indicate that the severity and spatial extent of aridity and drought have increase substantially in northwestern China in recent decade.We show that the drought intensification in northwestern China is mainly caused by the increase of evaporation which results from the continuous rise in temperature,which will pose a continuous threat to the ecosystem and economic development in this region,especially under the background of global warming.