The invention irons out the defects of conventional line lightning protection measures, and provides a new lightning-protection trip automatic arc blow-out parallel gap system for a power distribution network. The system comprises a voltage detection unit, a control unit, two metal electrodes, and an automatic arc blow-out unit. The two metal electrodes are respectively electrically connected with two ends of an insulator, and a voltage detection unit is disposed on the metal electrodes. A signal output end of the voltage detection unit is connected with a signal input end of the control unit, and a signal output end of the control unit is connected with the automatic arc blow-out unit. The system is wide in application range, can adjust the distance of parallel gaps of different power distribution lines, and can achieve the flexible adjustment of the lines with different relay protection parameters. Arc extinguishing energy comes from lightning, and there is no need to obtain additional energy from a line or in other modes. Finally, the system can flexibly adjust the switching time of a coil according to the size of different lightning overvoltages, and guarantees no tripping while releasing the lightning overvoltage.