[Objective]This study aimed to explore the temporal and spatial distribution of theoretic water requirement of crop in Aksu River irrigation area.It would be the theory evidence for water resources management and high efficient utilization.[Methods]Based on the daily weather observation data of 6meteorological stations during 19722014,the research was carried out using the correction model of Penman-Monteith which was recommended by FAO.The reference crop evapotranspiration(ET_0)were calculated,and the spatial data interpolation was executed.The theoretic water requirement of crop in Aksu River Irrigation Area was discussed based on the dimension of temporal and spatial.[Results](1)Annual mean ET_0was between 1 118and 1 241mm.It showed a trend of gradually increasing from the northern area to the southern area. (2)The value of ET_0 was the highest in spring and summer.The total value of ET_0 was 533mm in the months of May,June and July,aperiod having the most need for water supplement.(3)Yearly reference crop evapotranspiration showed a trend of gradually decrease since 1970s,and a significant decreasing trend after 2010s.(4)The ET_0variation presented a S-type curve,after the year of 2014,it showed an increasing trend.[Conclusion]The theoretic water requirement of crop showed a significant change over time in Aksu River Irrigation Area in the context of climate change.Spring and summer were the critical periods of irrigation. It showed a fluctuated and inclined steadily trend.Zone differentiation characteristics were obvious.