Abstract
The engine overall conceptual design plays an important role in engine design and to a certain degree its quality determines the overall quality of engine. Base on the parametric, simplified 3D model library of main parts and components and the exemplified assembly models of engine built by modern method, the authors analyze and design the engine overall conceptual design CAD system by the object-oriented method and then develop and realize the system in the VC++5.0 and Open I-deas developing environment. Finally, its practicability and reliability have been proved by some examples.