Unfried and fried oils were analyzed and studied by synchronous scan fluorescence spectra and combined with infrared absorption spectra. Synchronous scan fluorescence gave a narrower and simpler spectrum and was of extensive use for multi-fluorescence analysis. In this method,both excitation and emission monochromators were scanned simultaneously keeping a fixed wavelength interval (△λ) between them ( constant △λ mode). In experiment,the optimization △λ was 10 nm. The synchronous scan fluorescence was obtained in the emission wavelength range of 250 nm～700 nm. Compared with fresh oils,in the fluorescence spectra image of fried oils,fluorescence peak value in 370～380 nm disappeared,and two fluorescence peak value in 461 nm and 479 nm emerged. In 1745 cm^－1,the intensity of infrared absorption increased. All of this indicate that the number of carbonyl ( C = O) increased,which was the same to chromatogram approximately.