Urban public emergencies now break out frequently, causing heavy losses and threatening urban sustainability at the same time. To help better curb public emergencies, minimize their damage to cities, and maintain the sustainable operation of the city, this paper takes the urban public emergency as the research object, discussing the formation mechanism of urban public emergencies and putting forward feasible countermeasures. First, we propose the concept of risk propagation chain and construct an urban socio-technical system risk propagation chain model by introducing the Tropos Goal-Risk framework. The risk propagation chain formation mechanism and the emergency formation mechanism are researched by using this model to analyze the specific...