Abstract: With the development of strong and smart grid and the emergence of the Energy Internet,the deep integration of power grids and communication/information systems has become a necessity.Some systems’ blackouts have shown that communication/information failures（including natural faults and malicious attacks）affecting security and stability of the power grid are increasingly apparent.And this impact will keep rising in the future power grid.Thus,in the power grid blackout defense,the impact of communication/information security must be taken into account.The paper proposes the concept of three defense lines for the communication/information system first.Based on this concept,the communication/information security defense system is built with the functions of risk early warning and failure control strategy decision support.Then the framework of the power grid blackout defense system integrating power grid defense and communication/information defense is presented.And the method of coordinating power grid emergency control and communication/information preventive/emergency/corrective control is discussed.The new blackout defense system has been tested through a provincial power grid to show that after taking into account the communication/information and its risk,the control strategies from the blackout defense system have become more efficient,more reliable and more economical.