Abstract: To assess the influence of secondary measuring system faults on primary system, wide-area measurement system faults are considered in system faults based on the definition of “power-information” system scenario set. The observability of abnormal condition is analyzed for WAMS faults. By combing with the index of loss rate of power supply EDNS, the comprehensive reliability evaluation model of primary and secondary system is built. Based on Monte Carlo simulation, the results show that WAMS faults have great impact on power system and can not be neglected. Through the redundant configuration of PMU, the reliability degree is modified, which has great significant for improving the reliability of whole power system.