Abstract: A method for determination of phenolic compounds in diesels was established by using liquid-liquid extraction combined with gas chromatograph equipped with oxygen selective flame ionization detector（GC-OFID）. Diesel samples were first extracted with 10% sodium hydroxide. The extracted water phase was neutralized to Ph 5-6 with dilute hydrochloric acid and then re-extracted with dichloromethane. The phenolic compounds-containing dichloromethane were evaporated to get concentrated phenolic compounds and were then detected by GC-MS and GO-OFID. The structures or types of 54 peaks or groups of phenolic compounds were identified by GC-MS, chromatography retention time and boiling points. Benzyl alcohol was added into the concentrated samples as internal standard for quantification test. When 50 mL diesel sample is treated，the detection limits of phenol，2，5-dimethyl-phenol and 2，3，5-trimethyl phenol are 0.5，1.0，1.5 mg/L respectively. The relative standard deviations of five consecutive results are less than 8.0% in the phenolic compound concentration range of 8-40 mg/L，which meet the requirement of routine analysis.

Key words: phenolic compounds, diesel, oxygen selective flame ionization detector, gas chromatography