A coaxial gas-discharge tube belongs to the technical field of primary of electricity and gas elements. The tube body is formed by electrodes and components made from insulation materials, and the tube body is filled with inactive gas. The electrodes of the utility model are designed as an inner electrode and an outer electrode, to greatly improve the using frequency of the gas-discharge tube in the existing arresters. The outer electrode forms a cylindrical tube wall of the tube, and round sealing plate disposed at the two ends of the tube body is made from insulation materials. The inner electrode is a pillar body of which the two ends pierce a coaxial through-hole arranged on the sealing plate, and the inner electrode is fixedly installed in the tube body via a location step disposed on the pillar body. With the inner and the outer electrodes being positioned outside the tube body, the inner and the outer electrodes are capable of being in series connection with a coaxial inner conductor of an arrester conveniently, and then an upper limit of 300-megahertz operation frequency can be obtained. Besides, the utility model has the advantages of low inserting consumption, small voltage standing wave, small electrode capacitance, clash resistance, heavy current, long durability, wide ranges and the like, and thereby the utility model is applicable to protections of instantaneous over-voltage of various information systems.