The solubility of diethylammonium diethyldithiocarbamate (Et2NH2DDC), which is used as a chelating agent, in supercritical carbon dioxide containing ethanol as the co-solvent was measured with the dynamic method in the pressure range 10-30 MPa at 308.2-328.2 K. A new method using Peng-Robinson equation plus the modified Schwartzentruber and Galivel-Solastiouk and Renon mixing rule was proposed for the correlation of the experimental data. The properties of the solute, which are necessary for the correlation, were obtained by using the estimation methods. Compared with the classic Peng-Robinson equation with van der Waals II mixing rule method, the proposed model can correlate the solubilities with higher accuracy. The experimental data was well regressed by this new method.