In the past 50 years,due to the impact of climate change as well as high - intensity agricultural production activities,the fragile eco - environment of dryland in north China has been deteriorating,and there is a clear trend of degradation of dry farmland ecosystem. Ecological water shortage is one of the important reasons of ecological degradation. The article has discussed the trends of ecological water shortage in dry farmland ecosystem under the background of climate change in Wuchuan county (a typical county in dryland agricultural areas). The results show that the climate was gradually giving way to dry warming trend,especially in the past 20 years,the trend was more pronounced. From 1991 to 2010,ecological water shortage showed an increasing trend,for potatoes it was 45. 99mm/10a,and spring wheat was 55. 40mm/10a. Precipitation was the major factor affecting ecological water shortage. In the context of dry warming trend,ecological water shortage increased with the decreasing precipitation. That is to say climate change exacerbated the dry farmland ecosystem degradation. In dryland,it is important to pay attention to the degradation of dryland agro - ecosystem under the background of climate change.