The utility model provides a communications optical cable detecting device based on electromagnetic method. It includes signal transmitter and signal reception analysor, wherein signal transmitter with wait that it is connected to survey the communications optical cable for apply alternating signal on the communications optical cable to waiting to survey, the signal reception analysor is magnetic field detection and analysis device for the receipt is waited to survey the secondary magnetic field that the communications optical cable produced, and determines the concrete position of waiting to survey the communications optical cable through the analysis. The utility model provides a communications optical cable detecting device based on electromagnetic method's beneficial effect: optical cable, the uninterrupted communication system that at present moves are sought to nonvoluntary excavation slot, and on the basis of guaranteeing existing system steady operation, the effective recognition communications optical cable fully reduces the fortune peacekeeping fault handling's that the sign is unclear, record document confusion causes the degree of difficulty, promotes fortune peacekeeping fault handling's work efficiency.