Abstract: According to the characteristics of the nature of unexpected events, the number of incidents is in line with discrete random variables, and its loss caused by the disaster is a continuous random variable. It should consider the two variables for analysis, and compound extreme value theory can just meet this demand. It builds compound extreme value distribution model based on the compound extreme value theory, which uses two variables: the frequency of unexpected events and the resulting catastrophe losses for the emergencies. It gets the relationship between x_R and \lambda , or x_R and T through the analysis of the model The model provides a theoretical basis for the establishment of emergency preparedness systems, which has some reference value for other problems .