Abstract: A method of FT-IRS for determination of hydrogen fluoride (gaseous state) in tungsten hexafluoride was proposed and the installation of manifold for sample introduction was designed.Based on its IR-spectroscopic property,hydrogen fluoride behaved to show 8 characteristic absorption peaks in the the wave number range of 3 600-4 300 cm-1,among which the wavenumber of 4 038.2 cm-1 was chosen as the peak site for determination of hydrogen fluoride in order to avoid the interference of water steam.Standard reference gas of hydrogen fluoride was used for preparation of standard curve for the determination,taking volume fraction (φ/%) of HF(g) as the abscissa,and values of absorbance at 4 038.2 cm-1 as the ordinate.Linear relationship was kept in the range of 1.0×10-4%-1.0×10-3% for HF(g).