Abstract: The gas discharge lamp contains a lamp body and an UV unit. The UV unit contains a separate airtight chamber wrapping around at least a neck member of the lamp body and covering at least a part of a Mo tinsel inside the neck member. The airtight chamber is filled with one or more gases capable of being ionized, and is wound by a conductor whose one end is connected to a conduction wire extended out of one of the neck members. When the gas discharge lamp is turned on, the gases in the airtight chamber are ionized to produce an UV light to penetrate the discharge chamber. The gas discharge lamp therefore could have a lower starting voltage and an improved starting efficiency. Additionally, as the airtight chamber provides a heat insulation effect, the temperature-induced stress is thereby reduced.