On November 4， 2006， at around 22:10 the European interconnected grid was affected by a serious incident originated from the disconnection of a 380 kV line in the North German grid. The paper provides a brief description of the pre-fault system operation and of the main events that triggered the blackout， identifying some of the main causes that resulted in the separation of the European power grid and the blackout. In addition， issues related to the European power grid and lessons on the blackout are discussed. Some relevant measures are proposed to prevent large-scale blackout and construct the security defensive system in bulk power grid in China.