[Objective] Crop water requirements and effective precipitation are fundamental indicators for assessing the water supply and demand of crops. Climate change significantly impacts agricultural production. Investigating the characteristics of water supply and demand for major crops in Yan'an City can provide references for the water requirements of crops and the structure of crop planting in the region. [Method] This study is based on daily meteorological observation data from meteorological stations in the Yan'an area from 2000 to 2020. The FAO-56 formula and crop coefficient method were used to study the characteristics of water requirements, effective precipitation, and irrigation water demand during the growth period of major crops (spring maize, spring millet, potatoes, and winter wheat) in the region. [Results] From 2000 to 2020, spring maize in the Yan'an region had the highest water requirement and effective precipitation during the mid-growing stage, which were 247.85 mm and 68.34 mm, respectively, with a water deficit increasing at a rate of 6.61 mm per decade. Potatoes also had the highest water requirement and effective precipitation during the mid-growing stage, which were 288.83 mm and 89.53 mm, respectively, with a water deficit increasing at a rate of 5.75 mm per decade. Spring millet had the highest water requirement and effective precipitation during the mid-growing stage, which were 248.29 mm and 71.68 mm, respectively, with a water deficit decreasing at a rate of -7.0 mm per decade. Winter wheat had the highest water requirement during the rapid development stage, at 192.98 mm, with effective precipitation peaking in the early growth stage at 31.14 mm; the water deficit increased at a rate of 9.94 mm per decade. This indicates that even when effective precipitation reaches its peak, there is still a deficiency in water demand for crop growth. [Conclusion] It is necessary to reduce the planting area of spring maize and increase the planting area of spring millet and potatoes to improve the structure of crop planting. Additionally, increasing on-farm water collection measures can enhance the efficiency of rainwater resource utilization, ensuring food production and sustainable agricultural development in the Yan'an region.