Abstract: Based on a proposed model concerning the start-up process in multicom-ponent distillation with consideration of the hold-up in top, plates and re-boiler of the column as well as the plate efficiency, the computed result for a ternary system shows that the component concentration profiles in liquid during the start-up period are different in comparison with a binary system. Computations are confirmed experimentally by a pilot distillation column of 170 mm in diameter with methanol-ethanol-water ternary system.