Abstract: The spectrum and radiation intensity from visible to infrared light of a pulse Xe-lamp was measured in this paper. It showed that the flash intensity in the visible light spectrum of the Xe-lamp is above 1.30×10⁷ cd, the radiation intensity in the infrared spectrum from 0.8 to （3.2 μm） is 1.16×10⁷ W/sr, and the average flash time is about 0.2 ms. The behaviors of photo-detector PbS under intense flash were studied by taking the Xe-lamp as a simulated light source. It was found that the saturated threshold of photo-detector PbS under intense flash was about 6.79×10^-4 W/cm². The invalid time of photo-detector PbS under intense flash, and the effective distance between the light source and the photo-detector were also discussed.