Abstract: The study was conducted to investigate the effects of bioregulator coronatine (COR) on the development of plant shoot and root morphological parameters, and evaluate the regulation of leaf areas, chlorophyll contents and soluble protein content in maize (Zea mays L., cv. Jinhai 5) seedling under field conditions. The maize plants were treated with seed dressing or foliar spraying at V3 stage using different COR concentrations.The regulation of different concentrations of COR on the morphology in maize seedling showed that low concentrations of COR promoted seedling growth, but high concentrations of COR inhibited the growth. Seed dressing or foliar spraying with 0.1 mg/L COR promoted the plant height and the stem diameter growth, increased the leaf area per plant, improved the chlorophyll and soluble protein content in leaves, and enhanced the dry matter accumulation. Thus, COR promoted the maize root growth, increased root length and root surface area, which could effectively increase the absorption ability of the root. These results suggest that COR treatment may be a good strategy for strong seedlings cultivation in maize, by enhancing leaf photosynthetic performance and root absorption ability, which promoted the growth of shoot and root in maize seedling.