In this paper,agricultural machinery common parts are taken as the research object for parametric design based on CATIA.The parametric design based on CATIA has a variety of forms.The first is to use the knowledge engineering module in CATIA for the parametric design,this method is simple,but the call is more troublesome.The second is to build a catalog database design based on the parametric model built in knowledge engineering,the method is conductive to calling of the parts,but it requires a substantial amount of inputting data.The third is to use the CATIA secondary development technology to build parametric design.Building 3D model as a template based on knowledge engineering is a simple method in various method of CATIA secondary development technology.Designer can develop a computer-aided design software by extracting the main parameters of the parts based on VB language for the key parts.The method improves the design efficiency of parts,but it requires a certain programming foundation to designer.Parametric design is essentially a rapid design.Parametric design using CATIA secondary development technology for agricultural machinery parts can improve the development efficiency and mechanical performance.