Optimal utilization of resources has advanced the ever-increasing scale of power system interconnection and at the same time increases the degree of difficulty in keeping secure and stable operation of large power systems. An important technological countermeasure out to improve large power system stability is to construct an integrated and coordinated defense system. This paper analyzes key techniques in the engineering implementation of such a system， describes the current situation of its industrial application in China including its technical features and main application functions and expounds its role of enhancing the secure operation and control capability of large power systems.