Abstract: To investigate how calcium relieves cadmium toxicity in maize, the effects of exogenous Ca²⁺ on growth properties, photosynthetic characteristics and chlorophyll fluorescence parameters of maize seedlings under cadmium stress were studied in a pot experiment. A treatment with 100 mg/L of cadmium obviously inhibited the growth of maize seedlings, decreased the biomass of plants, and decreased the contents of chlorophyll a, b and a+b of leaves. At the same time, the net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), the maximal PSⅡ efficiency (F_v/F_m), photosynthetic electron transfer rate (ETR), the efficiency of excitation energy capture by open PSⅡ centers (F_v'/F_m'), photochemical quenching coefficient (qP), and the actual PSⅡ efficiency (Φ_PSⅡ) were reduced whereas the intercellular CO₂ concentration (C_i) and non-photochemical fluorescence quenching coefficient (NPQ) were increased under cadmium stress. Supply of exogenous Ca²⁺ under cadmium stress promoted the growth of seedlings, increased the biomass of plants and raised the contents of chlorophyll a, b and a+b of leaves. At the same time, P_n, G_s, T_r, F_v/F_m, ETR, F_v'/F_m', qP and Φ_PSⅡ of leaves tended to be increased with increased exogenous Ca²⁺ concentration, but C_i and NPQ were reduced. Among different Ca²⁺ application rates, 7.5 to 10.0 mmol/L Ca²⁺ had the greatest alleviation of Cd toxicity effects. It is suggested that Cd stress led to a decrease in the photochemical efficiency of PSⅡ, reduction in electron transfer, and reduction in net photosynthetic rate. Exogenous Ca²⁺at appropriate concentrations had favorable effects on seedling growth, including enhanced performance of the photosynthetic apparatus and capture of solar energy, effectively ameliorate Cd-induced depression of photosynthesis and enhancing the resistance of maize seedlings to Cd stress.