In order to reduce the communication traffic of wide-area backup protection (WABP) and improve the fault-tolerance capability of fault identification, this paper proposes a new algorithm of WABP based on fault correlation coefficient. After power grid is fault, the master station ranks the sequence voltage proportional coefficient from substations in order to identify the candidate fault line. Then master station obtains the action information of protection and direction component of candidate fault line and adjacent line to calculate fault correlation coefficient of line. Lastly, the master station integrates the fault correlation coefficient of line and compares it with the given threshold value to identify the fault line. The simulation example shows the new algorithm has small wide area communication traffic and high fault-tolerance capability and can significantly improve the performance of WABP.