城市化进程的加快导致公共场所人群聚集事故时有发生，试图用泊松分布来描述一段时间内事故发 生次数及其对应的概率，进而推导出事故灾害频率的定量模型；同时通过统计不同严重程度（死亡人数）事故 的发生次数，用其发生频率表征其发生的条件概率，根据计算得到的死亡事故发生概率，即可得到不同死亡人 数事故的发生概率，最终得到F－N图。运用F－N图就可以分析公共场所人群聚集的社会风险。以公共场所 部分事故统计为参考数据，描述使用该模型的步骤，结果表明该模型具有一定的合理性和准确性。

As the development of cities becomes more quick,  the accidents happened in public venues resulted form massing crowd become more and more.  This paper uses social risk to quantify the risk. On one hand,  in terms of former research outcome,  the paper deems that the occurrences of the accidents in public venues,  in a time span, can be described as Poisson distribution, and then, the quantitative model of accident occurrence probabilities can be reasonal out. On the other hand, through the sum of the occurrences of accidents of different severity level, which is to embody the situational probability of accidents of different severity level with its frequencies,  the outcome of accidents mortalities will be obtained,  which is used to figure out the probabilities of the accidents of different casualty numbers. In the end,  the F - N curve will be achieved. To use the F - N curve,  it is able to analyse the social risk of crowd massing venues.  Taking some statistical accidents as references,  it describes how to use the model.  The result proves the model is reasonable and accurate to a certain extent.