A novel method of high performance liquid chromatography with pH dependent fatty acid based dispersive liquid-liquid microextraction was proposed for the determination of three polycyclic aromatic hydrocarbons(PAHs),ie.phenanthrene，pyrene and acenaphthene.The parameters affecting the extraction efficiency were optimized.Under the optimum conditions of 55 μL n-heptanoic acid,50 μL 28%(mass percentage) NH4OH,500 μL 98%(mass percentage) H2SO4 and 3 min of centrifugation,three PAHs in water samples such as tap water,well water and sea water were determined by isocratic elution of acetonitrile-water.Results indicated that the calibration curves for three PAHs were linear in the range of 20-500 μg/L with correlation coefficients not less than 0.999 3 and detection limits(S/N=3) of 9.18-13.11 μg/L.The spiked recoveries for the analytes at three spiked levels were in the range of 87.9%-110% with relative standard deviations(RSD) not more than 3.0%.This method realized the enrichment and detection of PAHs with fatty acid as extractant.The method was simple and rapid,and was applied in the quantitative determination of PAHs in water samples within only 6 min.