The high precision thermostatic chamber is a specially designed constant temperature room with air as the heat transfer medium. It has the technical characteristics of high temperature control precision, good uniformity of temperature field and small fluctuation. There are many temperature measuring instruments that cannot come into contact with a liquid constant temperature source and are not suitable for calibration in a constant temperature bath. The emergence of high-precision constant temperature box solves the calibration problem of such instruments, fills the gap of constant temperature source, and provides a complete solution.