A diagnosis method is proposed in order to improve the accuracy of the analysis concerning remote control defects. The method is based on the monitoring of information flow and the parsing techniques of message, focusing on the systematic, procedural, accidental characteristics in the actual remote control operation. Through the monitoring system of substations and the data of remote information flow interactions, the key information of Ethernet transmission layer and application layer is captured in the abnormal remote control process, followed by the analysis of positioning control failure. The method solves the problems of remote control connections, complicated technology and difficulties in reproducing the faults. The whole process and full coverage of monitoring records and parsing message on information flow find the trace of the remote control failure, which also provide the technical basis for accurate defect diagnosis and the treatment plans. It is proved that the diagnosis method based on the monitoring of information flow and the analysis of the message is effective. Especially, it has a great advantage on the analysis of remote control defects, which is worth popularizing.