A quartz heater tube consists of a tube body whose two ends being respectively sealed with a plug, and each plug is provided with a built-in electrode. The inner cavity of the tube body is filled with an inertia gas after being evacuated, and the inner surface thereof is coated with a layer of electrical film which being electrically in connection with the two electrodes. By this construction, when the quartz heater tube is in operation, the electrical film is able to avoid oxidation owing to protection of the inertia gas which serves to isolate the electrical film from the outside air thereby prolonging the lifespan of the quartz heater tube.