Discriminating winter wheat-summer maize distribution is fundamental for agricultural water resources management in the North China Plain (NCP) which confronts severe conflicts between food production and agricultural water scarcity. However, how the planting area changed since 2000 is still unclear. Therefore, the winter wheat-summer maize from 2001 to 2018 was identified by using the maximum likelihood algorithm of supervised classification based on the Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) product. Three schemes with different temporal resolutions of MODIS data and sample categories were compared to obtain the most reasonable identification results. The results reveal that using 16-day 0.0025° MODIS NDVI data and six sample categories including winter wheat-summer maize, winter wheat-rice, spring maize, cotton, other one cropping systems and other double cropping systems is an effective way for tracking the variation of winter wheat-summer maize distribution. The winter wheat-summer maize planting area showed an insignificant increasing trend at a rate of 34.2 km²/year (p = 0.955, CV = 7.49%) during 2001–2018, while it decreased at the rate of −5065.2 km²/year (p = 0.074) after 2012. Spatially, the planting area shrunk in northern NCP, the piedmont plain of the Taihang Mountains, the west of dry sub-humid zone and the southwest part of the NCP, accounting for 58.6% of the counties during 2001–2018; while 17.3% of the counties significantly expanded winter wheat-summer maize in the irrigation district along the Yellow River in Shandong province, the southeast of Hebei Plain and the central humid zone. Our results provide fundamental information for quantifying the change of crop water consumption and optimizing crop water resource allocation.

在面临粮食生产与农业缺水严重冲突的华北平原（NCP），区分冬小麦-夏玉米分布是农业水资源管理的基础。然而，自2000年以来种植面积如何变化仍不清楚。因此，采用基于中分辨率成像光谱仪（MODIS）归一化差异植被指数（NDVI）产品的监督分类的最大似然算法对2001-2018年冬小麦-夏玉米进行识别。比较了MODIS数据和样本类别不同时间分辨率的三种方案，以获得最合理的识别结果。结果表明，利用 16 天 0.0025° MODIS NDVI 数据和包括冬小麦-夏玉米在内的 6 个样本类别，冬小麦-水稻、春玉米、棉花、其他一作和其他双作系统是跟踪冬小麦-夏玉米分布变化的有效方法。冬小麦-夏玉米种植面积以34.2平方公里的速度增长，增幅不显着² /年（p = 0.955，CV = 7.49%）在2001-2018年，而在2012年之后以-5065.2 km ² /年（p = 0.074）的速度下降。太行山前平原、亚湿润干旱带以西、华北西南部，2001-2018年占县的58.6%；而在山东省沿黄河灌区、河北平原东南部和中部湿润区，有17.3%的县明显扩大了冬小麦-夏玉米种植面积。我们的研究结果为量化作物耗水量变化和优化作物水资源配置提供了基础信息。