Pedestrian facility planning and pedestrian flow management and control depend on the theory of pedestrian flow. Simulation of pedestrian evacuation flow is presented based on cellular automata （CA） in this paper. Two dynamic parameters are formulated to simplify tactically the decision-making process of pedestrians, which can reflect the pedestrian judgment on the surrounding conditions and decide the pedestrian’s choice of action. The relationships of evacuation time against pedestrian density and exit width for different sizes of systems are studied. Moreover, the effect of exits arrangement on evacuation time is analyzed. It is observed that there is a linear relationship between evacuation time and pedestrian density, however, there is a negative exponential one between evacuation time and exit width. And exits arrangement affects pedestrian evacuation time.