In this paper, taking the mapping of reducer as an example, the two courses of mapping and computer graphics are com- bined organically, the characteristics of each component part of reducer are analyzed in detail, and various operation commands in- volved in the drawing process of reducer parts by using the computer graphics software AutoCAD are discussed. Through the reduc- er parts drawing and assembly drawing, the students’computer drawing skills are cultivated, and the application ability of combin- ing theory with practice is enhanced.