Abstract: Similarity algorithm was used for the gasoline oil spill identification. The chromatogram information was first converted to a two-dimensional vector, and the similarity between two-dimensional vectors was then calculated by the angle cosine method, by which the similarity of oil spill fingerprint chromatograms can be measured. The extracted oils referring as E-1, E-2 from two gasoline+water samples (C-1, C-2) from different FCC units were used as simulated oil spills. The results showed that the similarity between E-1 and C-1、E-1 and C-2 is 0.996，0.974 respectively, The similarity between E-2 and C-1、E-2 and C-2 is 0.983, 0.992 respectively. It is clear that the similarities difference between extracted oils and its corresponding original gasoline (E-1 and C-1, E-2 and C-2) can clearly distinguish two different gasoline samples. In the case of the repeatability limit method and t test method invalid, the original oil corresponding to extracted oil can be recognized accurately by similarity calculation method.

Key words: oil spill identification, similarity calculation, fingerprints chromatography