Objective:This paper establishes a high performance liquid chromatography for the determination of isosorbide-5-mononitrate(ISMN) in human plasma using carbamazepine as the internal standard.Method:a variable wavelength UV detector and Nuclbosil 5 silica 100A column(250 mm×4 6 mm, 5 μm ) were used. The alkalinized plasma sample was extracted with 3 0 mL methylene chloride . After evaporation of the organic layer, the residue was dissolved in mobile phase and injected onto a column. The mobile phase of methylene chloride-hexane-acetonitrile-methanol(92∶4∶1 5∶2 5) was pumped at 2 0 mL·min -1 through the column. The detector at 0 005 AUFS was set at 234 nm.Results:The retention times for ISMN and carbamazepine were 6 4 min and 7 0 min respectively. Standard curve was linear in the concentration range of 25 to 1 600 μg·L -1 . The detection limit in plasma was 10 μg·L -1 ; and method recovery was 96%～104%; within day RSD less than 4 5%; inter-day RSD less than 5%.Conclusion:This method was found to be simple, rapid, sensitive and accurate for determination of ISMN in human plasma.