To address the insufficient quantitative characterization of the relationship between cropping systems, phenological information and irrigation water demand (IWD), this study utilized phenological data of staple crops in China from 2000 to 2019 to characterize cropping systems, growth stages and crop rotation patterns. Based on the normalized difference vegetation index, potential evapotranspiration and precipitation data, the IWD was estimated using the crop coefficient method, and its linkage with cropping systems was quantified. The results show that the IWD exhibited significant spatiotemporal heterogeneity, with interannual fluctuations ranging from 65.9 billion to 127.3 billion m³. High-IWD years were generally synchronized with drought events, and high-IWD regions were concentrated in high-intensity multiple-cropping regions, such as the Huang-Huai-Hai Plain and the middle-lower reaches of the Yangtze River. Due to the significant spatiotemporal mismatch between the peak crop growth periods and the peak precipitation period, the IWD showed distinct seasonal peaks from May to August. The mean unit-area IWD of the wheat-maize rotation system was consistently higher than those of other cropping systems from 2000 to 2019, making it the dominant factor influencing the spatial distribution of IWD.