Abstract: The paper proposes a concept of space-time congestion to describe the congestion level of moving objects in time and space dimensions. Based on this concept, an emergency evacuation route optimization method is proposed. This method has the capability of providing an integrated solution for the evacuees to evacuate from their locations inside of buildings to the safe areas passing by road networks. This paper analyses the space-time congestion in the evacuation process based on the Dijkstra’s shortest path algorithm, and then optimizes this plan by virtue of resolving congestion and reducing the clearance time of the overall evacuation process. Experimental testing of this proposed method shows the optimized plan can ease the congestion of the evacuation plan systematically, and provide a relatively reasonable evacuation path for every single evacuee.