Abstract: There are many computer algorithms available for performing multicomponent distillation calculations,however,most of them are rating type algorithms(i.e.the number of equilibrium stages,reflux ratio,loca-tions of feeds,side—draws and intermediate reboilers are fixed in the calculation),they are not suitable fordesigning a new column.In this work,the authors have proposed a new design algorithm by applying optmization techniques.Based on the specified separation requirements and the chosen criterion of optimization,a set of optimumparameters can be determined through a single calculation.A hybrid method(tridiagonal matrix and 2N Newton-Raphson)was used in the rigorous distillationcalculation loop,and thermodynamic model(BWRS or PR)was coupled for performing VLE and enthalpycalculations.This new algorithm has been tested on five typical complex fractionating columns(including three fieldoperating columns),close agreements with original design parameters were observcd.