Lightning protection method and lightning protection device of ground-connection-free communication device with equipotential connection

The invention discloses a lightning protection method and a lightning protection device of a ground-connection-free communication device with equipotential connection. A telephone line protection module is connected between the communication device and a signal wire. A power supply protection module is connected between the communication device and a power supply module. A signal end protection module comprises a tripolar gas discharging tube G2, two poles on the outside of the tripolar gas discharging tube G2 are respectively connected on a signal end port. The power supply protection module comprises a piezoresistor TMOV1, a piezoresistor TMOV2 and a gas discharging tube G1, and a piezoresistor TMOV1 and a piezoresistor TMOV2 are connected in series and then connected onto the power supply module in parallel. One pin of the gas discharging tube G1 is connected between the tow piezoresistors, and the other pin of the gas discharging tube G1 is connected with a middle electrode of the tripolar gas discharging tube G2. The lightning protection method designs a power port and a signal port of the communication device into equipotential connection and resolves the problem of common mode and difference mode protection of the signal wire inlet side of the communication device and the power supply.