The effect of the adsorption of exogenous La 3+ on cation exchange capacity and solution composition in red earth was studied.Results showed that the adsorption capacity of red earth to La 3+ and desorption of adsorbed La 3+ were high.When the concentration of exogenous La 3+ was less than 400 mg/kg,the non exchangeable ratio of adsorbed La 3+ was higher than 50%.Cation exchange capacity(CEC) did not changed significantly with the increasing of exogenous La 3+ .When the concentration of exogenous La 3+ was higher than 300 mg/kg,base saturation percentage(BSP)and effective cations exchange capacity(ECEC)decreased significantly,exchangeable acidity and exchangeable aluminum,however,increased significantly compared with the control.The amount of exchanged base cations(Ca 2+ ,Mg 2+ ,K +,Na +)by La 3+ in supernatant solution increased with the increasing of exogenous La 3+ ,and showed significant difference when the concentration of exogenous La 3+ was higher than 50 mg/kg.