Startup of distillation columns is one of the most difficult operations in the distillation process. Although the design and control of divided wall column (DWC) is mature recently, the startup procedure for divided wall columns still suffers a lack of knowledge. This paper investigates a startup policy of a pilot divided wall column used for high purity separation of an aromatic reformate. The aromatic reformate contains benzene, toluene, ethylbenzene, p-xylene, m-xylene, and o-xylene. Very high product purities above 99.95 wt% are specified. The proposed startup procedure is consisted of four steps, including total-reflux, benzene withdrawn, toluene withdrawn, and continuous feeding. This startup procedure has been successfully applied to the DWC pilot plant used for high purity separation of the aromatic reformate. Temperature and composition profiles of each step are presented. These profiles are used for determining the switching points of the near two steps and understanding the dynamic behaviour of the DWC.