Welding device and welding method thereof

The invention provides a welding device which is used for welding a capillary tube to an auxiliary tube and comprises a main tube, multiple branch tubes, inflation nozzles, electromagnetic valves, pressure monitoring assemblies and a control assembly. An air inlet is formed in the main tube; one ends of the multiple branch tubes are arranged on the main tube; the inflation nozzles are arranged atthe ends, away from the main tube, of the branch tubes; the electromagnetic valves are installed on the branch tubes; the pressure monitoring assemblies are installed on the side walls of the inflation nozzles; and the control assembly controls the electromagnetic valves to be switched on or off through the pressure, monitored by the pressure monitoring assemblies in real time, on the side walls of the inflation nozzles, and then controls the circulation of cooling gas in the branch tubes. The invention further provides a welding method of the welding device. The cooling time is shortened by introducing the cooling ga