There are a growing number of crowded stampede events all over the world in recent years, which have seriously threaten the healthy development of modern cities. Therefor this paper has recorded crowded stampede cases for nearly 16 years. Basing on the event system theory, and combining with the characteristics of the event to analyzes the mechanism of the accidents, establishing the mechanism figure of stampede events, then put up the prevention and the methods of risk evaluation for the model of events. The stampede cases are happened under the event with strength special time and great influence to the organization. We should take consideration of event strength, event space, event time in the daily work and do more effort in the three aspects.