Potexperiment, laboratory culture and the sequential extraction procedures for the speciation of Cd in soil and plant were used to study the effects of calcium carbonate (CaC03) addition on transformation of cadmium (Cd) species in a brown soil added with Cd and change of Cd forms in leaves of maize. Compared to no CaCO₃ addition, CaCO₃ addition could lower content of exchangeable Cd, but increase the specifically adsorbed Cd, Cd bound to iron and manganese oxides, and residual Cd in the soil significantly. In presence of CaCO₃, soil pH, and [Ca²⁺]and [Ca²⁺]/[Cd²⁺]in saturation extracts increased, while [Cd²⁺]decreased, significantly. It was also found that dry weight and total Ca content of roots, stems and leaves of maize significantly increased, while the contents of total Cd, extractable Cd(H₂O, 2mol L^-1NaNO₃, 10%HOAc and 2mol L^-1HCl) and residual Cd obviously decreased with adding CaC0₃. It was concluded that Cd toxicity in soil-plant system could be alleviated by CaC0₃ addition.