Salinity is an obstacle to global agriculture, as it affects plant growth and development. Chitosan (CTS) has been suggested as a plant growth regulator to alleviate environmental stresses. In this study, the morphological and biochemical responses of chitosan application (75 mg L⁻¹) on maize seedling growth under salt stress (150 mM) were conducted with a hydroponic experiment. The results exhibited that CTS application effectively recovered salt-inhibited biomass accumulation and root architecture by increasing chlorophyll content and photosynthetic assimilation and reducing sodium content in shoots and roots by 25.42% and 5.12% compared with NaCl treatment. Moreover, salt-induced oxidative stress was alleviated by CTS application by increasing the activities of antioxidant enzymes of superoxide dismutase, catalase, ascorbate peroxidase, peroxidase and content of ascorbate. Correlation analysis and partial least squares (PLS) analysis revealed that root morphology and ascorbate play key roles for maize seedlings in response to salt stress. Based on these results, CTS application is recommended as an effective approach to enhance the tolerance of maize seedlings under salt stress.