Abstract: According to the analysis of the characteristics of oscillation paths in the optical cavity of the unstable-resonator DF chemical laser, we point out that different oscillation paths of the upstream and downstream spectra will lead to certain difference in the emission spectrum. The emission spectrum of a continuous-wave DF laser was measured, and it is found that there is no significant difference in the major spectral line components, but some difference in the relative intensity of the upstream and downstream spectral lines. The spectral band of the upstream laser spot, namely the rotational quantum number at maximum relative intensity, tends to be in the direction of the low rotational quantum number for each spectral band. According to the measured spectrum, the cavity temperature and particle population ratio were estimated, and it is found that the average temperature of the upstream cavity is lower than that of the downstream cavity.