Abstract: Fourier-transform infrared(FT-IR) emission spectroscopic technique has been establi-shed to study metal oxide catalysts. An in situ infrared emission cell was specially de-signed to treat sample in vacuo or in various gases at a wide temperature range (r.t. -700 ℃). Infrared emission spectrum of MoO_3 was presented and the results demons-trated that FT-IR emission spectroscopy is a sensitive method to detect vibrational information of metal oxide catalysts.The experimental conditions including sample preparation, effects of temperature and sample thickness on the infrared emission spectrum were detailed. It was found that the spectrum was severely disordered when the sample thickness of MoO_3 was beyond 1.00 mg·cm~2 and the more intensive emission bands were detected at higher temperatures. Infrared emission spectra recorded in the course of H~2 reduction of MoO_3 showed that surface linkage Mo—O—Mo species giving the band at 880 cm~(-1) is more easily reduced comparing to the terminal Mo=O species giving the band at 990 cm~(-1), vice versa, the Mo=O species are preferentially formed than the Mo—O—Mo species during the reoxidation of the partially reduced MoO_3.