This paper presents a dynamic traffic simulation method to forecast future traffic situation on congested road networks. The method is based on the continuous fluid model, and shock wave is considered in the basic formation. The model was made simple and capable of parallel processing for practical use on large scale networks. The model also includes how to deal OD structure of demand, merging and diverging, and route choice. Using some examples, dynamic behaviors of traffic flow was examined, and it was made clear that the model can represent the growth and decline of traffic congestion properly.