From the point of time and space, the social emergencies are divided into four types in this paper: longdistance and shorttime; longdistance and longtime; shortdistance and longtime; shorttime and shortdistance. Based on three factors such as material environment, social environment and mainstream information which affect the decisionmaking on group behaviors, this paper discusses the reason for the time interval and space distance for the emergence of social emergencies, and finally advances the preventing of time and space of social emergencies.