Urban operation safety will be the fundamental requirement for the success of the 2022 Olympics and Paralympics Winter Games in Beijing. Natural disasters often affect the urban infrastructures and lead to operations risks. This paper proposes a risk assessment method of the urban disaster chain based on Bayesian networks. First, according to the risk identification of natural disasters in winter in Beijing, a risk tree for disaster chain is constructed, considering the characteristics of natural disasters’ concurrency and coupling, and the relationships between natural disasters and infrastructure accidents. Then, in order to determine the hazard of the disaster chain, the Bayesian network method is employed to calculate the probability and severity of each event node in the disaster chain. Finally, taking the disaster of cold wave as an example, a quantitative risk assessment is conducted by the risk assessment method based on the index system, indicating that the method is feasible for the risk assessment of urban disaster chain.