In allusion to the influence of traffic flow change on vehicle routing selection, the article aims at finding the method for planning the trip route under the condition of knowing traffic flow change. The method combining particle swarm algorithm and dynamic planning is used for routing optimization in order to obtain the excellent route for various vehicles influenced by traffic flow. The road network structure and the traffic data in actual environment are adopted for simulation and the result shows that this method can truly and dynamically optimize routing, and meanwhile the road traffic flow and the travel time of vehicles can also significantly influence the routing selection of vehicles.