Energy characteristics of the reaction kinet ics of H⁺ -Ca²⁺ on red soil surface under acidic conditions were investigated by using a home-made dynamic device.The results showed that Ca²⁺ adsorption could be divided into rapid and slow reactions.The maximal Ca²⁺ adsorption fitted by the first order equation remarkably decreased with increase in acidity and reached equilibrium in advance with increase in temperature.A two-constant equation could be used to describe unevenness of the energy distribution of Ca²⁺ adsorption on the sites of the soil surface.Activation energy(Eb) of Ca²⁺ diffusion was calculated by using b value of the rate constant of Parabolic Diffusion Low and increased with increase in acidity,which reflected that the energy barrier to be overcome by Ca²⁺ diffusion would rise up and the rate of diffusion in Ca²⁺ adsorption decrease accordingly.Enthalpy of activation(H) was positive in value and rising temperature could contribute to Ca²⁺ diffusion.Entropy of activation(S*) was nagative in all cases,suggesting that system could improve its degree of order.pH of effluent drast ically dropped when the influent solution was pH 4.5 and pH 5.6.H⁺ release could be best described by the first order equation and the power-function equation,which were followed by Elovich equation,Parabolic Diffusion Low and zero order equation.Energy barrier to be overcome by H⁺ (Al³⁺) diffusion in pH 5.6 treatment was lower than that in pH 4.5 treatment.△H values of H⁺ diffusion were positive indicating an endothermic reaction and the increase in temperature speeded up H⁺ diffusion.There was the consumption process of H⁺ ion by using influent of pH 3.5,which was attributed to soil buffer mechanism and specific adsorption of SO₄^2-.The energy of activation of H⁺ consumption was lower than that of H⁺ release,showing that more H⁺ was diffused to the surface of soil particles than H⁺ released to bulk solution when the amount of H⁺ in the bulk solution exceeded a certain quantity.H⁺ consumption was rapid at the initial stage of the reaction.△H of H⁺ consumption,in comparison with that of H⁺ release,could contribute to H⁺ adsorption.Since H⁺ dissolution of minerals became a controlling process,it could be best described by Elovich equation and Parabolic Diffusion Low.