In order to provide the basis for the genetic improvement of density-tolerant varieties， the characteristics of ear traits were investigated in maize hybrids under different planting density conditions. Twelve maize hybrids that were popularized in China from four different eras since the 1980s were used in this study. From 2017 to 2018， these hybrids were cultivated in Shenyang city， Liaoning province and Gongzhuling city， Jilin province， with the two planting densities of 60，000 plants/hm² and 120，000 plants/hm²， using split plot experiment design （four row plots， three replicates each）. Ear length， ear diameter， bald tip length， rows per ear， kernels per row， and 100-kernel weight were investigated after harvest. These maize varieties showed extensively significant differences on rows per ear， kernels per row and 100-kernel weight. Ear diameter， bald tip length and 100-kernel weight decreased under different planting densities with the decades， while ear length， rows per ear， and kernels per row did not change significantly. The bald tip length was observed with especially significant difference， for example， with the average decrease of 0.24 cm （high planting density） and 0.19 cm （low planting density） every 10 years from 1980s to 2010s. Under higher planting density condition， shorter and thinner ear， longer bald tip and reduction on kernels per row were observed. New varieties released since 2000s became tolerant under higher planting density condition. For example， the ear length of 2000s new varieties and ear diameter of the 2010s new varieties decreased the lest， while the bald tip increase of the 2010s new varieties was the least with the value of 1.04%. In the future breeding for new high-yield varieties that are applicable under higher plant density， it is necessary to synergistically improve the ear length， ear diameter and bald tip， without a reduction on higher 100-kernel weight.