<p>The functionality of the road network after earthquakes is crucial for maximizing rescue efficiency. However, the existing regional road network vulnerability assessment methods still cannot effectively guide the design of a high-rescue efficiency network. In this context, this paper proposes the regional multi-state road network model combining the population distribution, multi-state characteristics of road infrastructures, and real network topology. Based on this, this paper proposes the post-earthquake road network vulnerability assessment method from the perspective of external rescue supply support capacity. Then, the proposed method is applied to two real regional road network cases. Finally, the post-earthquake road network vulnerability mechanisms and road network planning methods with low vulnerability can be explored by comparing different network models in various cases. In addition, this paper observes significant heterogeneities in post-earthquake road network performance loss caused by different roads, explained by road vulnerability and the availability of alternative routes. The road network design with alternative routes has lower vulnerability and higher supply capacity. Furthermore, accurate quantification of road network performance requires considering multi-state characteristics and real network structure, especially in dense road networks. This research provides important insights into road network modeling and design for earthquake rescue.</p>