The invention discloses a Fourier infrared spectrum detection device for high-humidity pollution gas. A water vapor spectrum with different water vapor concentration and close to target water vapor concentration is measured according to the work target water vapor concentration of the used drier; when a pollution gas spectrum is measured, the pollution gas passes through the drier repeatedly by adopting one inner circulation gas path design, the water vapor concentration of the pollution gas is reduced to be close to the target water vapor concentration of the drier, and the pollution gas spectrum at the moment is measured; two water vapor spectrums of the pre-measured water vapor spectrums with different water vapor concentration are automatically selected by a computer, the water vapor concentration of the two water vapor spectrums is closest to the water vapor concentration of the pollution gas and is higher and lower than the water vapor concentration of the pollution gas, and thewater vapor spectrum of the pollution gas is fitted by the two water vapor spectrums; and the water vapor spectrum is subtracted from the pollution gas spectrum, the water vapor absorbing peak in thepollution gas spectrum is eliminated, and gas pollutants with feature absorbing peak positioned in a water vapor area in the pollution gas are detected accurately.