Dividing wall columns (DWCs) are one of the most popular units in the recent separation technology due to their high energy efficiency and low capital cost. This paper proposes a design method of DWC for separation of silane off-gas in the polysilicon manufacturing process, and the controllability of optimized process was investigated using dynamic simulation. The results show that the DWC can save 36% of the energy consumption and require smaller number of total stages. Especially, the total annual cost was reduced up to 17%. The method and concept proposed here will provide a basis for optimal design of other DWC systems.