Transmission system is the important annulus in car factory total assembly workshop automation equipment. By applying the fieldbus technology, it made more reliable transmission system operation, maintenance convenience, which also greatly reduced the overall cost. For patients with the automobile assembly workshop, this paper combined with the development of fieldbus, introduced profibus-DP fieldbus characteristics, which based on the design of Siemens S7-300 programmable control system and profibus fieldbus technology car transportation equipment control system.