An ultra performance liquid chromatography-photodiode array detector (UPLC-PDA) method was developed for the determination of ibuprofen and the solubilizer arginine in ibuprofen injection. 2,4-Dinitroflurobenzene (DNFB) was used as the precolumn derivatization reagent. The separation of ibuprofen and arginine derivative was performed on a BEH C18 column (50 mm x 2. 1 mm, 1.7 microm) with the mobile phase consisting of acetonitrile-0. 05 mol/L potassium dihydrogen phosphate (pH 2. 5) in a gradient elution mode at a flow rate of 0.4 mL/min. Ultraviolet absorption detection wavelengths were set at 357 nm for arginine derivative and 220 nm for ibuprofen. The column temperature was set at 30 degrees C. Good linearities were obtained in the ranges of 2.0 — 100.5 mg/L for ibuprofen and 1.7 — 84.5 mg/L for arginine, both with the correlation coefficients (r) of 0. 999 7. The spiked recoveries were 99. 8% and 99. 6% with the relative standard deviations (RSDs) of 0. 37% and 0. 25% for ibuprofen and arginine, respectively. Their respective limits of quantification (LOQs) (S/N = 10) were 0. 1 ng and 0. 2 ng, and the limits of detection (LODs) (S/N= 3) were 0.03 ng and 0.05 ng. The results demonstrated that the proposed method is simple, accurate, reproducible and suitable for the quality control of ibuprofen injection.