Abstract: In recent years, the regional environmental risk caused by centralization of various kinds of petrochemical plants is increasingly significant, which urgently needs to be addressed to ensure the regional environmental safety. Based on the analysis of domino accidents risk among the installations at the regional scale, and integrated with the logical operation expressions for domino effect and the accident possibility calculation methods, the regional environmental risk assessment method was obtained in combination with the information diffusion method. In the case study, the method was used to assess the regional environmental risk of a city and the assessment results were visualized by the application of ArcGIS software. The results showed that the risk management departments should pay high attentions to three areas with extremely high risk, give high priorities when allocating management resources, and adopt mandatory measure to reduce the risks in these areas.