Abstract: Because the chain enterprise network is unique and the current main network security assessment model limitations,the paper proposed a chain business enterprise network security assessment model based on the networks similar domains.According to the chain enterprise internal network topological structure characteristics,the environment of the network is divided into similar security domain according to the security risk values,similar domain association is calculated,and network security risk values are quantitative evaluation.The network security assessment model is tested by experiments,the results show that,the proposed model not only has improved the risk assessment precision,but also reduces the amount of computation,it has a certain practicality.