The effects of several organic substances,including natural humic acid and fulvic acid,artificial chelating agents EDTA and DTPA,and four simple organic acids on the solubility and adsorption-desorption behaviors of purplish soil for cadmium were studied.Results showed that all the organic substances tested significantly promoted the solubility of cadmium from the purplish soil,with a magnitude sequence of EDTA≥DTPA>citric acid>humic acid>oxalic acid>fulvic acid>tartaric acid≥salicylic acid. These effects were attributed to their comprehensive influences on the adsorption and desorption of the soil for cadmium.Organic substances remarkably inhibited the adsorption of purplish soil for cadmium.The sequence of the inhibiting effects was as same as their influences on cadmium dissolubility.Desorption characteristics of absorbed cadmium were also altered by these organic substances.At the presence of organic substances the adsorption kinetics of purplish soil for cadmium was best fitted by the double-constant equation,and the curves of isothermal adsorption was best described by Freundlich equation.The adsorption constant n in Freundlich equation was well correlated with the dissolving rate of cadmium.