Abstract: This paper presents an approach to assessing the risk of cyber physical systems for distribution network considering communication failure in multi-agent system for power restoration.The proposed approach decomposes the entire power restoration process into multiple sub-tasks with inputs and outputs.When the communication system fails,sub-tasks that depend on the failed communication links will output an invalid value and will further influence the effect of power restoration.The expected loss of load of each failure state of power restoration system can be acquired by calculating the power shortage,recovery capacity and probability of each state.Hence the risk indicator of the cyber physical system for distribution network is established.The key communication links can be determined by calculating and comparing the sensitivities of the risk indicator to the packet loss ratio of each communication link.The reliability of the key communication links should be particularly enhanced during the design stage of communication system.Finally,the proposed approach is validated with a typical test distribution system.