This paper presents a new approach for preventing cascading outage by coordinated system and local monitoring and control scheme. System monitoring evaluates the vulnerability and security of the power system during dynamic changing conditions. It finds the vulnerable power system components indicating that their protective relays need to be monitored closely. Local monitoring can provide the exact disturbance information and monitor the correctness of the actual relay operations. If the relays act improperly, the proposed approach enables one to mitigate the disturbance or prevent the possible cascading outage. Further system control actions may be chosen based on the local information update. Several examples using the IEEE test system demonstrate the advantages of this approach.