Abstract: In order to solve the problem of temperature measurement method of flame temperature field and the lack of temperature measurement device in the tunnel type brazing furnace of air conditioning heat exchanger, a temperature measurement device based on thermocouple was designed and developed with the heat exchanger welding line of an air conditioning manufacturing enterprise as the application object. The specific form of flame temperature field in the tunnel brazing furnace was explored, which was used to measure the flame temperature field during the production of the production line. A mathematical model of the temperature field was constructed which fully showed the temperature field at the melting time of the welding ring on the workpiece. According to the temperature field model, the control mechanism of the technological parameters of the tunnel type brazing furnace was established to judge the distribution of the temperature field during the processing of the workpiece, which provided a scientific basis for the adjustment direction of technological parameters. The development of the temperature measurement device filled the vacancy of the automatic flame brazing temperature measurement mode of the air conditioning heat exchanger.The temperature field mathematical model established on this basis was more in line with the actual situation. At the same time, the mathematical model had a certain guiding role in the regulation of process parameters, which was conducive to process standardization and replication promotion.