With the expansion of China's power system, there are more and more factors contributing to Large-area Power Outages. The snow disaster that hit Southern China in 2008 caused serious damages to the power systems, which made Chinese government realize that they cannot solely depend on power enterprises to effectively control the risk involved in power system. The Chinese government needs to collaborate with power enterprises in strengthening Electricity Regulation and taking countermeasures to reduce the risk of Large-area Power Outages. This paper first proposes an objective, practical and adaptive Electrical Security Risk Assessment System based on Electricity Regulation. The system consists of an assessment process with 278 indices, which are used to calculate the risk of Large-area Power Outages by the use of Analytic Hierarchy Process and the Delphi Method. Then, an example of Guangdong power system serves to illustrate the detailed implementation procedures of the proposed assessment system and the results show that Guangdong power system faces a moderate risk of Large-area Power Outages. Finally, some countermeasures are proposed to overcome the defects in the existing power system. (C) 2011 Elsevier Ltd. All rights reserved.