Abstract: In order to analyze the indirect impact of flood on urban traffic, a model which named NetLogo is introduced to simulate the traffic situation of urban areas affected by rainfall. Two forms of traffic lanes, such as the two-way four traffic lanes and six traffic lanes, which are common in urban areas, are constructed by the model. By altering the different position of flooding on the road, such as at the starting point, the middle and the end of the road the changing process of vehicle speed can be observed at the same time. The results indicates that there are differences in the descent process of vehicle speed, when Vehicles traveling on the bidirectional four traffic lane and six traffic lane,but eventually the final speed tends to be same after stabilization. Otherwise, the maximum degree of vehicle speed variation appears when the flooding occurs at the starting point of bidirectional four traffic lane. the minimum degree of vehicle speed variation appears when the flooding occurs at the middle of bidirectional six traffic lane. The speed change process of vehicles traveling on the bidirectional six- lane is slower than that of the four- lane in the same situation when the flooding appears in different positions of the road. This study provides a useful reference for the research of the influence of urban flood on road traffic.