In order to investigate the physiological and biochemical mechanism of chitosan to improve the tolerance of maize seedlings to cadmium stress, we chose maize (Zea mays L.) cultivar ‘Zhengdan 958’ as experimental material and cultivated via Hoagland hydroponics in plant growth chamber. Maize seedlings were treated with chitosan of 100 mg·L^-1 under Cd²⁺ stress at different time points (0, 24, 48, 72, 96 h). The aim of this experiment was to examine the effects of chitosan on the antioxidant enzyme activities and endogenous hormone levels under cadmium stress. The results showed that: (1) under cadmium stress, the growth of maize seedling roots was inhibited, the generation of ROS was induced, the activities of antioxidant enzymes were increased, and the balance of endogenous hormones was destroyed. (2) After treated with chitosan under cadmium stress for 96 h, the dry weight of root increased by 16.1%, the generation rate of superoxide radical (O^-·₂) and the content of H₂O₂ in roots decreased by 9.1% and 19.2%, respectively. The activities of SOD, POD and CAT were increased by 32.5%, 20.4% and 21.3%, respectively, IAA, ZR and GA were increased by 34.4%, 40.4% and 42.5%, respectively, and ABA decreased by 19.1%. IAA/ABA, ZR/ABA and GA/ABA increased by 66.1%, 73.5% and 76.0%, respectively. The results indicate that under cadmium stress, chitosan could regulate the content and balance of endogenous hormones in maize seedling roots, reduce the damage of antioxidant enzyme system and enhance the ability to scavenge ROS. Thus, chitosan alleviated the toxicity of cadmium stress to roots and improved the resistance of maize seedlings. The study provided the theoretical and experimental basis for the application of chitosan to the cultivation of maize under stress.