A macroscopic dynamic traffic model for emergent incidents was presented with consideration of the number of the driveway, on-ramps and off-ramps and guidance instruction based on model METANET. And a bidirectional dynamic shortest path guidance algorithm for dealing with the emergent incidents timely and efficiently was also proposed. The weight altered dynamically with the change of the freeway and traffic jam. The shortest path from the two directions, which were timely and dynamically to strive for time in the processing of dealing with emergent incidents and succor, was searched. The simulation results show that the algorithm is feasible and effective and the efficiency of this algorithm has been improved.