Abstract: In the assembly drawing design of CAD, there are many functions to be implemented, such as parts inputting and positioning, hidden-line removal, graphics sectioning, guide-line layout, parts numbering and detail-list drawing, etc. Among them, the third and later ones are difficult to carry out automatically. To improve the automation of whole assembly drawing design, this paper presents some graphical recognition algorithms, for example, guide-line——number——part correspondence and sectioning area recogition in 2-D assembly drawing design. These algorithms can be also applied in other fields.