A gas soldering iron comprises a gas cylinder for storage of gas, a lower holder plate fixedly mounted on the gas cylinder at the top, which lower holder plate is connected with a T-shaped mechanism having set therein an elongated conduit tube and a movable tube to further match with a switching element, a gas jet cap, a spring and a revolving knob so as to control gas flow rate. The released gas from the cylinder through the T-shaped mechanism is further passing through a upper holder plate wherein the gas is mixed with the circulated air to further run through metal tubular element for producing a fire to heat the soldering head for performing soldering process.