The increasing population, water scarcity, and labor cost demand more high-yield, water-saving, and efficient maize production. Grain mechanical harvesting, the quality of which is mainly influenced by grain moisture content, can improve the efficiency and decrease the harvest cost of maize production. However, the cultivar, sowing date, irrigation schedule, and cropping system not only affect the yield and evapotranspiration of maize but also affect the quality of grain mechanical harvesting. Therefore, to achieve high-quality grain mechanical harvesting, increase the yield and save water, a method for optimizing sowing date and irrigation schedule of different maize cultivars in various cropping systems was proposed in this study, and used at a typical site in the North China Plain. The APSIM and a grain dry down model were used for optimization using meteorological data from 1961 to 2020. The latest date for grain mechanical harvesting of two maize cultivars in three cropping systems was first analyzed in different cropping systems using the date when the grain moisture content decreases to 25% for the first time (DCM25). The DCM25, yield, water use efficiency, and irrigation amount were used as constraints in the optimization of sowing date and irrigation schedule. The results showed that the optimal sowing date was from mid-May to early-June in most circumstances. The summer maize in winter wheat-summer maize double cropping system could not achieve high-quality grain mechanical harvesting with the two cultivars at the typical site. The cultivar with a shorter growth period, lower grain moisture content at maturity, and faster grain dry down rate and the increasing temperature were helpful for maize to achieve grain mechanical harvesting. In most years, the optimal irrigation schedule with grain mechanical harvesting involves irrigation (80 mm each time) one or two times during sowing and jointing stages of spring maize in the monocropping maize system and summer maize in the winter wheat-summer maize-spring maize system (three crops in two years, WMM) and irrigation for two or three times during sowing, jointing, and flowering stages of spring maize in WMM. The results of optimization could be used for similar sites, and the optimization method could be a reference for other sites to promote high-efficient maize production
