The invention discloses a gas discharge tube and an overvoltage protection device. The gas discharge tube comprises at least one insulator, at least two electrode assemblies and at least one electrodecoolant, wherein a through hole is formed in the insulator; the opposite surfaces of the at least two electrode assemblies form discharge surfaces; the insulator and the at least two electrode assemblies are enclosed to form a discharge inner cavity; the through hole communicates with the discharge inner cavity; and the electrode coolant is connected with one electrode assembly, the shortest distance between the surface, toward the discharge inner cavity, of the electrode coolant and the discharge surface of the electrode assembly is H and the value range of H is that H is smaller than or equal to 1.2mm and greater than or equal to 0mm. When an inert gas is subjected to arc discharge, the electrode coolant cools the electrode assembly connected with the electrode coolant, temperature riseof the discharge surface is delayed and burnout or short-circuit of the electrode assembly caused by overheating of the discharge surface is avoided, so that the security is improved.