To address the demand for precise testing of thin-film thermocouples in fields like industrial automation and aerospace, as well as the limitation that traditional tube furnaces fail to meet testing requirements—such as diverse morphologies and short distances between the reference junction and measuring junction—in thin-film thermocouple metrological testing, this study focuses on the design and application of a chamber furnace. Based on the Seebeck effect and thin-film thermocouple testing principles, the core requirements for the chamber furnace are defined: its internal space must accommodate irregularly shaped thermocouples, the temperature field fluctuation and gradient must comply with metrological testing standards, and the reference junction must be equipped with water-cooling temperature control. The chamber furnace designed accordingly features a furnace body assembled from thermal insulation components, three-stage molybdenum disilicide rod heating for temperature control, and a water-cooling device that can fix samples and standard thermocouples while monitoring the reference junction temperature in real time. Thermodynamic simulation results demonstrate that the temperature field at the sample's measuring junction and the temperature of the reference junction meet the design expectations. Furthermore, application tests are conducted, and the calibration practice of Au-Pt thin-film thermocouples further verifies its effectiveness. This furnace can provide reliable metrological support for the application of thin-film thermocouples in temperature detection under complex environments.