A method was developed for the simultaneous determination of bromoadiolone and brodifacoum in water by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and ultrasonic assisted extraction with ionic liquid ［C4mim］［PF6］.An ionic liquid,1-butyl-3-methylimidazolium hexafluorophosphate(［C4mim］［PF6］) was used to extract the rodenticides in water samples.The extraction parameters,including sample volume,temperature,ultrasonic-extraction time,inorganic salt concentration and solution pH were investigated.The separation of target compounds was performed on an XDB C18 (150 mm×2.1 mm,5 μm) column with methanol- 0.2% acetic acid(85∶15) as mobile phase.The detection was carried out by LC-MS/MS using a negative electrospray ionization interface in multi-reaction monitoring(MRM) mode.Calibration curves were linear within the range of 0.005-1.0 μg?L-1 with correlation coefficients more than 0.999.The limits of quantitation(LOQs)were both 0.005 μg?L-1.The extraction recoveries were between 91.0% and 97.8%,the intra-day RSDs were between 1.1% and 6.6%,and the inter-day RSDs were between 2.5% and 9.1%.The developed method was simple,accurate and distinctive,and could be used for the determination of trace bromoadiolone and brodifacoum in environmental water.