The invention relates to a quality method for a divided-wall column. The main objective of the invention is to overcome the technical problems of difficult operation and control, poor stability and hardly-controllable product quality and yield of conventional divided-wall columns. The quality method provided by the invention overcomes the above technical problems by controlling temperatures, flowrates and liquid levels in five control areas of the divided-wall column, i.e., a control area for raw material feeding, a control area for column-top reflux and extraction, a control area for liquidcollection and distribution, a control area for side-line extraction and a control area for column-bottom extraction. The quality method can be applied to industrial production of the divided-wall column.