A high temperature CO₂ flow field was set up in a high frequency plasma wind tunnel. The profiles of temperature and mole fraction were obtained through measurement and calculation. At the same time, infrared spectrum measurement experiment was carried out. The equipment, principle and method used in the experiment were given. Experiment was made under four different temperature conditions between 1500 K and 3000 K. The infrared spectral data of v₃ vibration band of CO₂ near 4.3 μm at different temperatures were acquired. It was found that the peak position of the spectral curve moved in the direction of long wavelength as temperature increased. Through theoretical analysis, the reason about the "red shift" occurred in the measurement of infrared radiation of CO₂ at high temperature and its difference from the red shift in astrophysics were obtained. This theory could be used in the measurement of high temperature gas.