Different unsaturated fatty acids have different physiological functions, however, the common fatty acid products are mostly mixture of several unsaturated fatty acids. Thus it is necessary to analyze the composition of impure fatty acid products before application. In the present article, the Raman spectra of oleic acid and linoleic acid (the most commonly appearing components of fatty acid products) were measured. Furthermore, the mode assignments of the Raman bands were determined and the molecular conformational characters were analyzed. The results lay the groundwork for researching the energy level structures and transitions of long-chain unsaturated fatty acids and enrich the valence bond data of organic molecules. In addition, the differences between the Raman spectra of oleic acid and linoleic acid were analyzed in detail, which provides a convenient and effective method for their identification and has directive significance for the application of Raman spectroscopy in hogwash oil detection.