Traditional Dijkstra algorithm has the defect of poor availability in route planning of expressway emergency evacuation. In order to solve this problem, an improved Dijkstra algorithm was presented, considering the characteristics of links and nodes with traffic restriction in expressway network.A new representation mode of nodes with capacity restriction and traffic volume calculation method was proposed. According to the characteristics of vehicles to be evacuated, a classified route planning method was proposed by filtrating the sections of expressway with height and weight restriction. Furthermore, based on an emergency evacuation case in Henan expressway system, a numerical experiment was estab⁃ lished and its problems were solved by using traditional algorithm and improved Dijkstra algorithm respectively.The result showed that the distributed traffic volume on upstream section was higher than the upper limit of node capacity in route planning and traffic distribution using traditional algorithm, which may lead to evacuation bottlenecks. Meanwhile, overweight vehicles weren′t able to be evacuated in sections of expressway with weight restriction. In comparison, there were no such problems above using improved Dijkstra algorithm, and the evacuation efficiency and the availability of evacuation route were improved by using the new method.