A rapid method was developed for the detection of 5 common fatty acids,including palmitic acid，stearic acid，oleic acid，linoleic acid and linolenic acid,in vegetable oils based on ultra-performance convergence chromatography-mass spectrometry(UPC2-MS).The sample was dissolved with n hexane，followed by clean up of extract using 022 μm organic phase filter.The fatty acids were separated in 3 min on a column of ACQUITY UPC2 BEH 2-EP(2.1 mm i.d.×100 mm,1.7 μm) by gradient elution with carbon dioxide and methanol-acetonitrile（by volume，1∶1）　system，and finally detected by MS detector.The results showed that the calibration curves of five analytes were linear in the range of 0.5-100 mg/L with correlation coefficients（r2） not less than 0.998 5.The recoveries for five fatty acids at three spiked levels were in the range of 90.5%-105.4% with relative standard deviations of 0.8%-2.9%.The limits of detection for the target compounds in the method ranged from 0.07 mg/L to 0.26 mg/L.In comparison with other methods，this method was simple,rapid,and had good separation effect.Furthermore，the method could provide reference for further research and application of UPC2 technology in oil related analysis field without derivatization of fatty acid samples.