The invention relates to a copper tube nitrogen charging and welding method and a nitrogen charging and welding control device. The welding method includes the following steps: a first step of parameter setting, a second step of welding, and a third step of last welding. In the parameter setting step, the pressure value of nitrogen charging is set no more than 0.05MPa, and a flow value of nitrogen charging is correspondingly set according to the cross section area of a copper tube. In the welding step, nitrogen is charged in the copper tube for welding according to parameters set in the first step. In the last welding step, flow of the nitrogen is reduced to no less than 1L / min. The invention further relates to the welding control device using the welding method. The welding control device comprises a nitrogen bottle, a pressure reducing valve, a pressure meter, a nitrogen pipe and a gas flow meter. In a practice base or a laboratory, according to the technical scheme, the oxidation phenomenon caused during welding of the copper tube is effectively prevented. The method and device can be popularized and applied to the industrial fields such as welding of air conditioner cooling pipelines, prevents an oxidation layer from being formed in a tube, reduces the fault rate of a cooling system, and improves quality of air conditioning products.