Currently, the research on Vehicular Ad hoc Networks(VANETs) is hot. Vehicular movement model is an important factor, which affects the simulation results of VANETs. In the simulation of VANETs, Vehicular movement model used in the urban environment should consider not only the characteristics of the vehicular movement, but also the role of obstructing the radio waves. In this paper, after a detailed analysis of vehicle motion features, it gives a vehicular movement model based on directed graph. The simulation shows that the model can well reflect the movement of vehicles in the real world, and the influence of urban environment on the network performance.