A light tube for a cold cathode fluorescent lamp includes a light tube body, anode and cathode disposed in the light tube body and an activated gas absorber. The light tube body contains inert gas, mercury substance and a layer of phosphor coating on its inner surface. The cathode is adapted for electrically connecting to the negative terminal for emitting electrons to excite the mercury substance for conducting the electrons to the anode as an electric circuit, wherein the excited mercury substance emits ultra violet rays causing the phosphor coating to generate visible light. The activated gas absorber is gas absorber made of zirconium-aluminum alloy which can be activated at an activation temperature substantially lower than 900 degrees Celsius, preferably 390 degrees Celsius, to provide stronger oxygenic gas absorption ability while reducing the manufacturing steps and cost.