The invention relates to a band gap puffer type medium voltage lightning arrester for an overhead distribution line, belonging to the technical field of an electric power facility element. The low-voltage part of the band gap puffer type medium voltage lightning arrester is connected with the low-voltage end of either the tower or the insulator of the overhead distribution line through a connecting base, and the high-voltage part of the band gap puffer type medium voltage lightning arrester is fixed on the overhead distribution line through a connecting support; the low-voltage part consists of a metal base and an insulating sleeve, wherein the lower end of the metal base is provided with a connecting base, a plurality of cavity electrodes and a plurality of arc extinguish chambers are sequentially and intermittently arranged in the insulation sleeve, blowholes for spraying high-speed gas are formed in the top of the extinguish chambers, and a low-voltage electrode is formed in the top of the insulating sleeve; the upper half part of the low-voltage part is exposed, a discharging gap is jointly formed by the low-voltage electrode and the high-voltage electrode, the high-voltage part consists of a high-voltage electrode and a connecting support, and a conductor grip is jointly formed by the high-voltage electrode and the connecting support. The lightning arrester provided by the invention is simple in structure, convenient to mount, definite in function, is capable of effectively cutting off discharging arc caused by the overvoltage of a circuit, and guaranteeing the reliability of a power system.