A calculation method of optimum parameters on dual adsorption isotherm system was examined. The optimum parameters were obtained by non-linear regression analysis based upon a limited solute concentration of dual adsorption isotherm. The results were analyzed with adducing experimental data of formerly reported treaties. The percentage mean deviation of dual adsorption equation calculated with optimum parameters was less than about 5% of experimental data, which was far less than results obtained with parameters of the adduced treatises.