An analytical method was developed for the simultaneous determination of trifluoroacetate and trifluoromethanesulfonate by reversed phase liquid chromatography with indirect ultraviolet detection using pyridinium ionic liquids as mobile phase additives.The chromatographic behaviors of the two anions on the C18 column were studied and compared with four types of reagents including pyridinium ionic liquid，imidazolium ionic liquid，4 aminophenol hydrochloride and tetrabutylammonium chloride as mobile phase additives.Effects of concentrations of pyridinium ionic liquids，organic solvents and detection wavelength on separation and detection of the anions were investigated.The role of ionic liquids，retention rules and relevant mechanisms were discussed.Pyridinium ionic liquids acted as ion pair reagent and ultraviolet absorption reagent in separation and detection of the anions.The separation of the anions was performed on a C18 reserved phase column using methanol-03 mmol/L N hexylpyridine bromide（10∶90，by volume) as mobile phase at a column temperature of 30 ℃，a flow rate of 10 mL/min and a detection wavelength of 250 nm.Under these conditions，two anions were completely separated in 12 min.The detection limits were 009 mg/L and 018 mg/L，respectively.The method was applied in the determination of trifluoroacetate and trifluoromethanesulfonate in ionic liquid samples with spiked recoveries of 960%-101%.The method is simple，accurate and practical.