Abstract: 【Objective】 To explore the effects of chemical control agent Yuhuangjin (30% prochloraz and ethephon ) on microstructure and flexural strength of spring maize stem. 【Method】 Jingnongke 728 and Jinnong 738 were taken as experimental materials, the stem bending strength, the microstructure of stem and the correlation and path analysis between the microstructure of vascular bundle and the bending strength of stem were carried out. 【Results】 The results showed that: the number of vascular bundles has the most direct influence on the bending strength of stem, there was an extremely significant negative correlation is -0.760; there was an extremely significant positive correlattion with xylem area, which is 0.970; it was positively correlated with the average area of single vascular bundle, the maximum diameter of vascular bundle and the thickness of epidermal cells 0.661, 0.659 and 0.632 respectively. 【Conclusion】 The number of vascular bundles of Jingnongke 728 and Jinnong 738 decreases per unit area at different planting densities after spraying 200 mg/L Yuhuangjin, but the thickness of epidermis increases, the maximum diameter of vascular bundle is the largest, the bending strength is improved, and the lodging resistance is enhanced.