Abstract: OBJECTIVE To establish an HPLC method to determine the concentration of linezolid in human plasma．METHODS With phenobarbital as internal standard, the protein plasma sample was precipitated with acetonitrile．The separation was carried out using Luna C₁₈ (250 mm×4.6 mm, 5 μm) column with mobile phase of acetonitrile-water (25∶75) at a flow rate of 1.0 mL·min^-1．The detection wavelength was 251 nm and the column temperature was 35 ℃．RESULTS The linear range was 0.1-40 mg·L^-1 (r=0.999 9), and the LOQ was 0.05 mg·L^-1. The intra-day and inter-day precision were both less than 4%. CONCLUSION The method is simple, sensitive, accurate and suitable for the study of therapeutic drug monitoring and the pharmacokinetic study of linezolid．