Sequestration of greenhouse gases into geological brine formation is one of the promising options for the reduction of greenhouse gases. Co-injection of both CO 2 and H 2S from flue gas may reduce the cost of carbon sequestration. The phase equilibrium of H 2S-H 2O was investigated with SAFT EOS. H 2S was modeled as a molecule with four association sites. For the H 2S-H 2O system, cross association between the site H in H 2S and the site O in H 2O was allowed, and a temperature-dependent binary interaction parameter was used to adjust the cross dispersive energy between the segments of H 2S and H 2O. The parameters of H 2S were obtained from the fitting of saturated vapor pressure and liquid density of H 2S. The model could be used to represent the phase equilibrium for H 2S-H 2O system from 273 to 630 K and ≤ 200 bar