Combining with the typical architectural design case, the book explains in detail the AutoCAD2012 mechanical design points of knowledge, and lets the readers know well of AutoCAD2012software operation skills in the process of studying the project and case making, and cultivate ability of Engineering design at the same time. The book is divided into 3 parts, with a total of 15 chapters. Among them, the first part is about the basic knowledge (1st- 4th), contains the AutoCAD201 elementary course, drawing and editing commands, text, tables and dimensioning, fast drawing tools; the second one is about the plane works of project case (fifth ninth), which contains the whole design process of reducer from the part chart to the plane image of the assembly drawing; the third one about the three-dimensional engineering drawings of project case(Tenth fifteenth), which contains the three-dimensional drawing basis, reducer parts from the chart to the assembly drawing three-dimensional engineering drawing design of the whole process. In addition, the book is accompanied by the use of AutoCAD2012 common command, which is convenient for the reader to inquire.