A computational mass transfer method for simulating extractive distillation process is proposed and applied to the simulation of an extractive distillation for the separation of benzene and thiophene mixture using N-methyl-2-pyrrolidone（NMP）as the extractive solvent. To testify the validity of the simulating method，experiment was performed under identical condition in a randomly packed column，in which the concentration distribution in the extractive distillation column was measured. The simulated results was found in agreement with the experimental measurement. It demonstrates that the proposed computational mass transfer method can be used to predict effectively the concentration and velocity profiles in an extractive distillation column.