In this paper, a multi agent system (MAS) based wide area protection and control scheme is proposed to deal with the long term voltage instability induced cascading trips. Based on sensitivity analysis between the relay operation margin and power system state variables, an optimal emergency control strategy is defined to adjust the emergency states timely and prevent the unexpected relay trips. In order to supervise the control process and further minimize the load loss, an agent based process control is adopted to monitor the states of distributed controllers and adjust the emergency control strategy. A hybrid simulation platform based on LabVIEW and real time digital simulator (RTDS) is set up to simulate a blackout case in the power system of Eastern Denmark and to demonstrate the effectiveness of the proposed MAS based protection strategy.Index Terms-Cascading trips, hybrid simulation platform, multi agent system, process control, wide area protection 0885-8977 (c) Denmark. His research interests include power system analysis and digital simulation, operation and control of power system, wide area protection system on modern power system, wind power integration.Zhe Chen (M'95-SM'98) received the B.Eng. and M.Sc. degrees from Northeast China Institute of Electric Power Engineering,