To achieve rapid new car developments and cost saving, new approaches for automotive general assembly in manufacturing preparations are needed. In this paper, CAD and DMU technologies for design and evaluation of machines and equipments are discussed. Digital Mock-up based on 3-D CAD models usually apply in the area of concept design and design review. We focus on manufacturing preparations of the machine and equipment. Detail procedures, examples and considerations of DMU are suggested in this paper. By applying DMU in the manufacturing preparations of general assembly, time, cost and quality of engineering can be enhanced through engineering collaboration.