Abstract: The study on the group dynamics,the influence of their proportion and scale on the pedestrian flow,the morphological characteristics and activity features in crowd is not adequate enough. This paper builds up a simulation platform to simulate different scenarios using the social force group model. Result shows that pedestrian group lowers the average speed of pedestrian and increases the crowd density. The larger the group size is,the lower the average speed is,and the more obvious the effect can be. With the growth of width of walking space,pedestrian flow shows a trend of increase. Pedestrian groups ensure more stable walking routes and walking speed. Although social groups decrease the efficiency of crowd evacuation,they do produce the "path effect".