Abstract: The water sample was passed through a 0.45 µm glass fiber filter membrane, and an aliquot (10 mL) was taken. Then, the 100 µL of 1 µg·L^-1 mixed internal standard solution was added. After mixing well, the mixed solution was passed through a 0.22 µm disposable polyethersulfone syringe filter. Perfluoroalkyl compounds (PFCs) in the filtrate were enriched using online dual solid phase extraction system and then introduced into ultra-high performance liquid chromatograph-triple quadrupole tandem mass spectrometer. Separation was performed on Waters BEH C₁₈ column using the gradient elution system consisting of acetonitrile and 2 mmol·L^-1 ammonium acetate solution. Mass spectrometric analysis was conducted in negative ion mode of electrospary ion (ESI) source with multiple reaction monitoring (MRM) mode, and quantification was achieved using the internal standard method. It was showed that linear relationships of the mass concentrations of the 19 PFCs and ratios of their peak areas to internal standard peak areas were kept in definite ranges, with detection limits (3S/N) in the range of 0.01-0.03 ng·L^-1. Spike recovery tests were performed using surface water, groundwater, drinking water, and industrial wastewater as matrices, giving recoveries in the range of 84.1%-118%, and RSDs (n=6) of the determined values ranged from 2.2% to 6.8%.