Abstract: The change of chemiluminescence in visible range in the optical cavity flow field of HF laser for different flow rates of D2 was observed and recorded, and spectra of the chemiluminescence on the optic axis were measured using the spectrometer calibrated with 632.8 nm and 543.5 nm He-Ne lasers. The components of the gas in the optical cavity were analyzed theoretically, and the high order overtone spectral lines of DF molecule and spectral lines of D atom were computed. The comparison of the measured spectra of chemiluminescence and the spectral lines shows that, the chemiluminescence is formed by the radiation of excited F, He, D, N atoms and DF, N2 molecules, and the excited state of other particles. The colour formation of the chemiluminescence on the optic axis wa