Abstract: An algorithm for multistage multicomponent separation calculations was presented for the extractive distillation columns including both the first column for separating C5 alkanes and alkenes from dienes and the second column for separating alkynes and cyclopentadiene from isoprene. Based on the equilibrium data of C5 hydrocarbons in the presence of solvents, the simplest linear equation was recommended for the vapour-liquid equilibrium relations log(yi-/yip) =log(vi/viP).xs where V represents activity coefficients, Y represents y at infinite dilution, x represents the molar fractions, and the subscripts i, ip, s represent i-compo-nent, isoprene and solvent respectively. Using this equation together with the T(temperature)-xs and the Yip-xs relation data, a calculation procedure proposed by Lu Huan-zbang[1] was employed with some modifications. The computations were carried out on TQ-16 computer for the above mentioned extractive distillation columns, and the results were compared with those obtained from a model column equipped with 92 sieve-plates and 9 sampling sites along the column. The above results - indicated that the calculated and experimental values agreed quite well with each other both for the first column with as many as about 20 components and the second column with components in ppm amounts. The average deviation was 0.36% for all components of the first column, 0.20% for main components of the second column, 27 ppm for components less than 1000ppm, and 0.9ppm for those less than 10ppm. The average deviation in temperature was 2.5℃ for the first column and l.3℃for the second. It may be concluded therefore, that the vapour-liquid equilibrium data and the proposed vapour-liquid equilibrium equation as well as the computational procedure employed were reliable for the calculation of C5 hydro-carbons-DMF extractive distillation.