PDMS/PAN composite membrane was prepared and employed in pervaporation separation of n-octane/thiophene mixtures at laboratory scale. At different initial thiophenes (thiophene and 2-methyl-thiophene) concentrations (corresponding sulfur contents about 500-2500 g/g) and feed temperatures (30-70 โข C), experimental results were carried out and average flux, selectivity and activation energy of permeation were calculated. It was found that increasing in temperature yields higher total fluxes and lower selectivity to thiophenes, while changing concentration of thiophens in the range concerned produces insignificant effect on total flux and selectivity. Experiments also showed that PDMS membrane is more selective to thiophene than to 2-methyl-thiophene and it may be mainly because of the difference in molecular size and structure. Total fluxes for thiophene/n-octane mixture and 2-methyl-thiophene/n-octane mixture were measured to be 1.5 and 1.4 kg/m 2 h at 30 โข C, with the corresponding selectivity to thiophenes 4.9 and 2.5, respectively. Based on simplified solution-diffusion model, the permeation fluxes of individual components in pervaporation of thiophene/2-methyl-thiophene/n-octane ternary mixture had been predicted and showed to be in good agreement with experimental values.