AutoCAD is widely used in the detail design of hull structure. However, the drawing efficiency is relatively low in the traditional planar design mode. Whereas, the automation of AutoCAD may be effectively improved to simplify some tedious plotting process by using the secondary development technology. A series of assistant functions for the plotting has been implemented by the secondary development of AutoCAD according to the characteristics of the hull structure together with the drawing standards, which improves the drawing efficiency of the hull structure drawing in many ways.