In order to meet the calibration requirements of the temperature acquisition instrument, a high stability large air temperature calibration test chamber was developed. The box structure and working principle of the test box are expounded. Based on the theoretical model of heat transfer process in the chamber, numerical simulation was carried out with Fluent software. The distribution and variation of temperature field and air velocity field in the chamber were analyzed. The test proves that the test box has high temperature control precision, small temperature fluctuation and good uniformity of temperature field, and can be popularized and applied.