A reversed-phase HPLC method has been developed for the separation and determination of naproxen and its bromo-substituted compound. These compounds were separated on a Shim-pack CLC ODS column (5 microns, 250 mm x 4.6 mm i.d.) by using a methanol-water (80/20, V/V) solution containing 50 mmol/L lactic acid and adjusted to pH 2.5 with perchloric acid as mobile phase, with flow rate of 0.8 mL/min and UV detection at 271 nm. Benzoic acid was selected as an internal standard. At the concentration range of 5-100 mg/L, the linear internal standard working curves with r > 0.9995 were obtained. The accuracy of this method for naproxen and its bromo-substituted compound were 99.83%-102.07% and 99.00%-100.83%, and RSD were < 2.58% and < 3.64% respectively.