Lodging resistance is a critical trait in modern maize breeding. This study aimed to examine maize stalk lodging and its related characteristics in response to increasing planting densities in modern hybrids. A two-year field trial was conducted from 2018 to 2019 with two widely grown commercial hybrids ('Xy335' and 'Fm985') and three planting density treatments of 4.5 × 10 (low density, LD), 6.5 × 10 (medium density, MD), and 8.5 × 10 plants/ha (high density, HD). New hybrid Fm985 had a significantly higher grain yield and lower lodging rate at HD, while there was no significance at LD and MD. Compared to Fm985, old hybrid Xy335 had a significantly high plant height, ear and gravity height, and culm length (CL) across the three planting densities, while opposite stalk bending strength (SBS), dry weight per unit length (DWPU), cross-sectional area, and the cellulose and lignin content in the basal internode were low. Correlation and path analysis revealed that kernel number per ear and lodging rate directly contributed to maize grain yield, while lodging-related traits of SBS, stem lignin, and DWPU had an indirect effect on maize grain yield, suggesting that modern hybrid maize yield enhancement is associated with greater stalk lodging resistance at a high planting density in northeast China.