The study aims to identify the degradation products of levofloxacin by HPLC-MS.  The degradation products of levofloxacin were chromatographed on Agilent Zorbax Extend-C18 column (250 mm × 4.6 mm, 5 μm).  The mobile phase was 0.1% ammonium acetate solution (using methanoic acid to adjust to pH 3.5)- acetonitrile at the flow rate of 0.5 mL·min⁻¹ (gradient elution), the column temperature was 40 ℃.  Descarboxyl levofloxacin, desmethyl levofloxacin and levofloxacin N-oxide were identified through comparing with the standard spectrum and the results of mass spectrometry, i.e. m/z 318.2 was descarboxyl levofloxacin, m/z 348.2 was desmethyl levofloxacin, m/z 378.1 was levofloxacin-N-oxide.  This method is simple, fast, accurate and suitable for the identification of degradation products of levofloxacin.