Abstract: Research on spatial propagation rules of traffic congestion is a significant foundation of traffic management and route guidance. In this paper,spatial nonstationarity of traffic datawas firstly studied, and then an analysis method of traffic congestion propagationwas also derived. Effectiveness verification of the improved model was embodied in the case of the road network of Beijing. The case studies imply that, traffic congestion happening on local road will spread to others, and the influence of propagation decreases with distance.The spatial influence of traffic congestion reaches the maximum in road networks with critical density. Therefore, closer supervision of the key nodes with critical-density status inthe network should be conducted to limit the spatial influence of traffic congestion.