Infrared spectroscopy (IR) and normal Raman spectroscopy (NRS) of Sudan red(Ⅲ) and Sudan red(Ⅳ), and surface-enhanced Raman spectroscopy(SERS) of them on Cu—Ag nanocomposite material were reported in the present paper. The density functional theory (DFT) calculation was applied to calculate IR and NRS on a B3LYP/6-311+G (d,p) level, and the theoretically calculated spectra were carefully compared with the obtained experimental spectra. The vibrational peaks were assigned by the software of Gauss view 5.0. Rapid identification of Sudan red was realized, which provided profitable basis for characteristics and quick test of Sudan dyes, and reliable detection method of food security.