Various denatured vegetable oils were classified into the original oils based on their fatty acid compositions determined by thermally assisted hydrolysis and methylation-gas chromatography in the presence of trimethylsulfonium hydroxide combined with multivariate analyses. As a whole, 132 oil samples subjected to discrimination were obtained from 11 types of vegetable oils after denaturation under various conditions such as indoor exposure under different lightings or denaturation during combustion. Here, peak intensities of the methyl esters of the representative five fatty acids observed in the chromatograms such as palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2) and linolenic (C18:3) acids were used as input variables for the multivariate analyses such as principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA). As a result, first, discriminative analysis among the oil classes was attempted by means of PCA. Although linseed oil samples were clearly differentiated from the other oil samples even after denaturation by developing the 1st and 3rd principal component scores, the distinct discrimination among the oil classes other than linseed oil was difficult. On the contrary, SIMCA was successfully used to classify every oil sample into their original vegetable oil much more distinctly even for those after denaturation.