The invention discloses an
infrared cavity ring-down
spectroscopy trace gas detection method based on
quantum cascade laser; comprising the following steps: using a tunable
quantum cascade laser as alight source, and selecting measuring waveband and
wavelength scan step length aiming at spectrum line characteristic of the gas to be detected; respectively measuring the cavity ring-down time of each
wavelength in the cavity with absorption or without absorption by cavity ring-down technique, and calculating the gas absorption coefficient of corresponding
wavelength so as to obtain a relation curve that is an absorption
spectrogram of the measured gas absorption coefficient and toned
laser wavelength. The
spectrogram is contrasted with spectrum line characteristic of corresponding gas in HITRAN
database, thereby being capable of analyzing and determining weather the measured gas contains the predetermined gas component; the
absolute concentration of the gas to be measured can be calculated and obtained and the
absolute concentration of the gas to be measured can be measured through scaling measurement by using absorption peak wavelength of the absorption spectrum as the best detection wavelength and the relation among the gas absorption coefficient of the wavelength, the
absorption cross section and concentration. The method has high measuring sensitivity and high property of resisting interference so that the fast and exact on-line analysis and detection of multiple trace gases are easily realized.