In the present paper a new approach is introduced to design a mechanical assembly on microcomputer.This technique uses Auto-CAD package as supporting software. It is composed of five modules. Two of them are interface programs, converting Auto-CAD drawing into data files or vice versa. A designer can input the proper components and set them on suitable "layers" by the component set module. The assembly drawing will then be displayed by running the edge-intersecting module and the hidden-line eliminating module. Finally, a focusing mechanism is employed to exemplify the developments mentioned above.