The invention provides a ground sign board, as well as a cable external damage preventing system and a cable external damage preventing method. When sensing that the vibration exceeds the specified displacement, a vibrating sensor inside the ground sign board generates pulse which triggers a device power supply control circuit, then a power supply is enabled to communicate with a processor and a communication module, the processor drives the communication module to send the serial number of the ground sign board to an intelligent terminal, the intelligent terminal carries out automatic searching according to the serial number of the sign board, displays the position and mounting time of the ground sign board and the information of the corresponding cable, and automatically marks the position of the ground sign board on a map, and thus a navigation route is established; and an operation and maintenance worker can arrive at the scene according to the navigation route at the first time for checking that whether the external damage risk exists or not. According to the technical scheme, the device power supply circuit is in conducting only when the sensor detects that the vibration exceeds the specified displacement, at ordinary times, only the consumption of the sensor and the self-consumption of a lithium battery are generated, the power consumption is extremely low, through powersupply of the lithium battery, the long-term use is available, and meanwhile, the device has the advantages of being waterproof and dampproof, being high in reliability, being simple in structure, being compact in size, and being convenient to mount.