Modeling and simulation for a sulfolane extraction process were performed. The process investigated in the present work consists of two tray columns, one of which is used for extraction and the other one for washing. The modified θ-method was employed for the modeling of the process. The computation of the equilibrium state of a two-phase system is one of the key issues in the modeling and simulation of extraction processes. In the present work the UNIFAC method was used for the computation of related thermodynamic properties and equilibrium states. Results of simulations showed good agreement with actual plant operation data.