The traditional shape design method of tractor is mainly completed based on the manual design. Messages are transmited mainly through material object, model, blueprint and template. The material object and model even have a small change that will cause massive chain-reactions such as tedious blueprint revision. And there will be a great many of problem, such as the development cycle of tractor to be long, the accumulative error of design to be big, the development cost to be high and product universalization and serialized degree to be low. This problem is key problem to be solved for shape designer. Advanced design method such as CAD/CAM provid solutions for us, and especially the concept of parametric design was applied. In this paper an appfoach for the parametric design of tractor configuration will be presented. To this end, there are two key issues to be solved: First, the parametric representation of the tractor configuration, second，how to generate a three—dimesional shape of the tractor automatically based on the parametric representation. The parametric design of the tractor configuration is implemented by making use of the API technique of the CAD software，namely automation in CATIA．The test example shows that the approach presented is able to generate a three dimensional shape of the tractor automatically and meet the need of the parametric design of tractor configuration.