With the secondary development to SolidWorks by VisualBasic, parametric design method for driving gear of EMUs motor bogie was researched, and plug-in unit system of SolidWorks was compiled, which realized automated design, parameterized modeling, and automated 2D engineering drawings renewal. Design and analysis speed was enhanced, and product-developing cycle was shortened. This method makes remarkable senses on parametric design of other typical parts which have the same structures and different size.