The invention discloses a method for monitoring road conditions in real time based on a simplified road network model and belongs to the field of road junction monitoring. The method comprises the following steps of: firstly, establishing the simplified road network model, abstracting ordinary intersections, traffic light intersections, overpasses and loops as nodes, abstracting a one-way road section between two nodes as a directed arc, abstracting a two-way road section between the two nodes as two directed arcs, and weighting at least one time cost weight value on each directed arc; secondly, periodically acquiring time at which a vehicle enters a starting node y and an ending node z and acquiring the information of the current position of the vehicle and the information of entering direction; and finally, determining the type of roads, and thus respectively obtaining the road condition states of ordinary roads, the loops and overpass roads by using different steps. By adoption of the method, the road condition states of the ordinary roads, the loops and the overpass roads can be simply and accurately obtained, and the road condition states are drawn on a map, so that the road conditions can be monitored in real time.