To accurately identify, in a timely fashion, a protection device that has been mis-operated in the installation protection system, and in order to ensure the safety of power system operation, a real-time analysis method of installation protection decision based on wide-area synchronous data is proposed. A measurement node is selected according to the network topology and the installation protection synchronization signal is detected. Protection indices are calculated based on the wide-area synchronization data. A fault identification function is established for overcurrent, distance and direction protection. Based on EMTP, a 38-node system is simulated, and a fault analysis function is calculated for the four types of fault conditions, and the correctness of the protection decision is verified by the function calculation result. The results show that the online analysis method of installation protection based on wide-area synchronous data is effective and practical, and the method can accurately identify decision errors in protection schemes. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 521304170028) and Science and Technology Project of State Grid Fujian Electric Power Co., Ltd. (No. 521304180013).