A method for determination of fatty acids in vegetable oil is developed by gas chromatography- mass spectrometry (GC-MS). Boride fluorine-methanol system is used to methylate the samples, and then the fatty acid composition is analyzed and identified by GC-MS. 11 kinds of fatty acids are identified. The results show that the main fatty acids are oleic acid, linoleic acid, palmitic acid, stearic acid, and the content of oleic acid and linoleic acid is more than 70%, the ratio of unsaturated fatty acid content to saturated fatty acid content is 5.9% corn oil, 17.6% rapeseed oil, 11.7% sunflower ...