Abstract: 【Objective】 The reference crop evapotranspiration combined with crop coefficient can be used to estimate the irrigation water requirement at each growth stage of crops, which might provide a basis for agricultural water allocation. 【Methods】 In this paper, the reference crop evapotranspiration (ET₀) was simulated by Hargreaves-Samani (H-S), Irmark-Allen (I-A) and Priestley-Taylor (P-T) methods in Aksu city of Xinjiang. The precision of the three simulation methods was evaluated according to R², nRMSE and MAPE, and the variation of ET₀ at interannual and monthly scales was analyzed. Different typical years were selected to analyze the water demand rules of winter wheat, cotton, spring maize and summer maize. 【Results】 (1) The R² of ET₀ calculated by Hargreaves-Samani method, Irmark-Allen method and Priestley-Taylor method were 0. 965, 0. 949 and 0. 946, respectively, and MAPE were 20. 85 %, 26. 46 % and 66. 71 %, respectively. (2) The 30-year average cumulative value of ET₀ in the study region was 960 mm, which was larger from May to August and smaller in December and January. (3) The irrigation water requirements of winter wheat, cotton, spring corn and summer corn were 108 mm, 308 mm, 131 mm and 136 mm respectively in the regreening-jointing stage, flowering-budding stage, heading-milk stage and heading-milk stage. (4) During the whole growth period, the water requirements of winter wheat, cotton, spring corn and summer corn were 448, 533, 394 and 385 mm, respectively. 【Conclusion】 H-S method and I-A method has good universality in Aksu city; the cumulative value of ET₀ in the study region did not change much between years, and it increased first and then decreased during the year; the key water requirement periods of winter wheat cotton, spring corn and summer corn were reviving-jointing stage, flowering-flocculation stage, heading-milk ripening stage and heading-milk ripening stage, respectively; during the whole growth period, the water requirement of cotton is the largest, followed by winter wheat, spring corn and summer corn.