In order to study the effect of chemical regulators application on lodging resistance of maize under high density conditions, and to clarify the mechanism of chemical regulators application on regulating stem lodging resistance, ‘Xianyu 335’ was used as experimental material and Yuhuangjin, Duntianbao and Zhuangfengling were sprayed respectively at the six-leaf stage. The agronomic characters, the stem mechanical characteristics, the content of cellulose, hemicellulose and lignin in stem and root, dry matter accumulation and yield of maize were analyzed. The results showed that Yuhuangjin, Duntianbao and Zhuangfengling significantly decreased the plant height,ear position height and center of gravity of maize, increased the third internode stem diameter, and the lodging rate decreased significantly. The puncture strength and bending strength of stem increased by 8.1%-23.3% and 7.8%-21.2% respectively. The lignin content of stem and root increased significantly, and the yield increased by 7.1%-11.6%. Chemical regulators application mainly reduced plant height and ear position height of maize, and then reduced the height of center of gravity, increased the diameter and the lignin content of stem, improved the mechanical characteristics of stem, so as to reduce the lodging rate and increased the yield of maize.