Abstract: A ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the determination of glufosinate-ammonium and its metabolites in coffee cherries was established. The samples were thoroughly homogenized and ultrasonic extracted with 0.1 mol/L ammonia water. After centrifugation, the supernatant was concentrated at 40 ℃, and dissolved with methanol-water solution (V:V=1:1). The sample solutions were separated by an ACQUITY UPLC BEH HILIC column with gradient elution in aqueous solution containing 0.1% formic acid, and detected on a tandem mass spectrometry operated in multi-reaction monitoring (MRM) mode and quantified with external standards. The results showed that the calibration curve was linear within the range of 0.1-2.0 mg/L with correlation coefficient(r) of 0.997, 0.998 and 0.991, respectively. The average recoveries of 3 compounds were 92%-107% at spiked levels from 0.05 mg/kg to 0.5 mg/kg, with relative standard deviations (RSD) between 2.0% and 4.9%. The limit of quantification(LOQ) was 0.05 mg/kg. The method simplifies the pretreatment, improves the recovery, and is suitable for the analysis of glufosinate-ammonium residue.