In the humid area of eastern Jilin Province, the response of maize stem and leaf traits and yield to plant growth regulators under dense planting conditions was studied using Dika 159, a variety with high yield potential, as the test material. The results showed that the plant growth regulator can reduce the plant height, ear of corn plant high, shorten the basal internode length, reduce the leaf area per plant, adjust the blade distribution of various levels, which in addition to the plant stem and leaf of redundant, reshape the ideal plant type, ensures the effective panicles, improves the spike grain number, finally achieving the target of production. Among all the treatments, the yield of the regulator treatment was the highest in the 8 spreading leaves, and the plant morphology with large leaves in the middle and lower leaves and small leaves in the upper leaves could be shaped, which was conducive to the acquisition and utilization of light energy.