At present, China's automobile logistics cost accounts for more than 20% of the production of motor vehicles. Therefore, lowering logistics cost by seeking its best path is an effective way to lower the cost of automobile manufacturing. This paper combines the Graph Theory and the genetic algorithm to research the optimizing problem of the lines of logistics distribution. Traffic flow data under normal conditions is obtained through field studies, based on which we can calculate the time of the network weight through appropriate method, find the best lines of distribution through the optimization theory of genetic algorithm, and show the feasibility and superiority of the method through examples.