Abstract: Global warming is an increasingly worrisome environmental and climatic phenomenon. Global average temperature increased by 0.60~0.70 oC over the last centuray, with an average temperature rise of 0.80~1.50 oC in China. Northwest China is one of the most sensitive areas to climate change. Temperature (a critical factor of global warming) is often used in an integrated method to calculate crop water demand. In other words, temperature afftects climate change, which in turn affects crop water needs. Crop water requirements in Northwest China is therefore critical in farm water cycle. It is also an important hydraulic and water-saving parameter in agricultural research, planning and design. This study addressed issues such as: the effect of climate change on agricultural water demand in different regions, and current lack of systematic and quantitative data to support crop water requirement research in the face of global warming. This study analyzed the effects of warming climate on crop water requirement in Gansu Province under different temperature scenarios (future temperature increases of 1~4 oC). The results showed that the effects of warming climate on crop water requirement were different for different crops. Warming climate greatly afftected water requirement of winter wheat, followed by spring wheat and maize. When future temperatures rose by 1~4 oC, water requirement of winter wheat increased by 3.05%~12.90%, which was the equivalent of 13.2~81.2 mm. That of maize increased by 2.49%~10.80%, the equivalent of 9.9~60.6 mm. Then spring wheat water requirement increased by 2.74%~11.69%, the equivalent of 6.7~40.0 mm. Regional differences were noted in the impact of warming climate on crop water requirement. The impact of warming climate on crop water requirement was highest for arid regions, followed by semi-arid regions, and then semi-humid regions. The least effect was for humid regions. When future temperatures rose by 1~4 oC, the temperature scenario caused additional irrigation water requirement of 1 243, 1 302, 1 374 and 1 465 million m³ for winter wheat; 794, 832, 878 and 930 million m³ for maize; and 497, 516, 542 and 576 million m³ for spring wheat, respectively. Warming climate worsened water shortage problems in the study area.