In pervaporation operation pore diffusion model predicts that a vapour-liquid pseudo-equilibrium exists between the solute concentration in vapour and liquid phases during its flow through the pores of the membrane. In the present investigation, using pore diffusion model an attempt has been made to predict a semi-empirical vapour-liquid equilibrium relationship for benzene concentration in vapour and liquid inside the pore of the membrane while separating benzene-cyclohexane azeotropic mixture by pervaporation technique.