In view of problems such as the high break rate of mechanically harvested summer corn in the Huang-Huai-Hai double-cropping area and the serious hindrance to the development of mechanized corn production, it is necessary to select corn varieties suitable for mechanical harvesting in this area. In this study, five main corn varieties planted in the double-cropping area were used as experimental materials, based on grain water content and dehydration rate, and a compression characteristic parameter was proposed as an auxiliary evaluation index for the suitability of corn harvest, and a quantitative method for the compression characteristic was developed. Further, by means of threshing experiments, the average breakage rate and the average unstripped rate of grains were used as evaluation metrics, so as to establish an evaluation method to characterize the appropriateness of grain harvesting. The results showed that under the same water content condition(33%±1%), DH605, LY296 and KN21 had high average grain breakage rates of 5.39%, 5.02% and 7.13%, respectively. They are slow to become dehydrated after physiological maturity, making them unsuitable for mechanical grain harvesting. LK868 and LD6018 have an average grain break rate of 4.76% and 4.25%, respectively, and an unstripped break rate of 0.83% and 0.84%, respectively. After physiological maturity, dehydration is rapid and suitable for mechanical grain harvesting. This study provides a reference for selecting suitable corn varieties for machine harvesting.