Abstract: As a protective tillage measure, subsoiling tillage is an effective control method for increasing maize density and yield and has good application prospects in China. However, researches on the effect of subsoiling on the dehydration characteristics of maize grains is lacking. Accordingly, we selected five representative maize hybrids from the 1970s to the 2010s in different eras, adopted two tillage methods, subsoiling tillage (35 cm deep) and shallow rotation tillage (15 cm deep), and set up a split plot test. The variations in grain dehydration characteristics before and after the physiological maturity of maize hybrids across different eras and their response to subsoiling tillage were investigated. The objective of the study is to offer theoretical support for the adoption of this practice in the context of mechanical grain harvesting. The results revealed significant differences in the grain dehydration characteristics of maize hybrids from different eras. The grain moisture contents at physiological maturity (MCpm) of the 2000s and the 2010s hybrids were lower than those of the other hybrids, whereas the grain moisture contents at harvest (MCh) of the 2010s hybrids were also lower than those of the other hybrids. The dehydration rates before physiological maturity (GDRbm) of the 2000s and 2010s hybrids were higher than those of the other hybrids. Compared with the traditional shallow rotation tillage, the decrease of grain water content in 15–35 d after anthesis increased, GDRbm had a small increasing trend, whereas the dehydration rates after physiological maturity (GDRam) showed no significant change under subsoiling tillage; and the effect of subsoiling on MCpm and MCh was small. Compared to shallow rotation tillage, the dehydration rates of the bracts and ear cobs under subsoiling tillage before and after physiological maturity decreased, whereas the dehydration rate of the ear stalks showed no significant change. In summary, the hybrids from the 2000s and 2010s demonstrated superior performance in dehydration characteristics for mechanical grain harvesting. Subsoiling tillage notably enhanced grain dehydration by primarily augmenting the reduction in grain water content in 15–35 d after anthesis. This resulted in a marginal increase in the grain dehydration rate before physiological maturity post-subsoiling along with a reduction in the dehydration rates of bract and ear cob both before and after physiological maturity following subsoiling tillage. However, there was no significant impact of tillage measures on the grain dehydration rate after physiological maturity or the water content of grains at physiological maturity and harvest stages.