Using computer to generate crowd animation to understand the behavior choice and making decision of individuals in crowd has become a trend in several fields. And group emotions have a great impact on group behaviors and group outcomes. Based on the researches of group emotions described by Hatifield, we propose a quantitative method to building the group emotion model which is focus on a group or a crowd, not on an individual. Our aim is to reflect more believable emotion experiences of individuals in social situation; the individuals’ emotion is coming not only from the external stimulus, but from others group members through the conscious and unconscious induction of emotion states as well. For the emotional contagion plays a significant role in the development of group emotion, we select personality, emotional expressivity and susceptibility as mainly factors which influence the intensity of group emotions. Simulation is done by using Netlogo software, and the results show that the model is available and embody the fundamental characteristics of group emotion, and virtual individuals in crowd can generate credible emotional experience and response.