An HPLC method for the determination of imatinib mesylate tablets was established.Kromsil C18 column (4.6 mm×250 mm, 5 μm) was adopted with 20 mmol·L-1 sodium dihydrogen phosphate containing 0.04% octane sulfonic acid sodium salt (adjusted pH to 2.5 with H3PO4)-methanol (40:60) as the mobile phase at the flow rate of 1.0 mL·min-1.The detection wavelength was 268 nm.The column temperature was 30 degree.The imatinib mesylate showed a good linear relationship within the range of 25.055-501.1 μ g·mL-1, r=0.999 9.All the RSD were less than 2%.The average recoveries were 99.54%-101.23%.This method was accurate, simple and rapid, and it can be used for the determination of imatinib mesylate tablets.