Abstract: The mask cosmetic sample was hydrolyzed under acidic condition, and then the obtained hydrolysate underwent derivative reaction with 1-phenyl-3-methyl-5-pyridinone. HPLC was applied to the determination of hyaluronic acid in mask cosmetics. Kromasil C₁₈ chromatographic column (250 mm×4.6 mm, 5 μm) was used for separation with mixtures of acetonitrile and 0.025 mol·L^-1 ammonium acetate solution with different mixing ratios as mobile phase in the gradient elution. UV detector was used in the determination. Linear relationship between values of peak area and mass concentration of hyaluronic acid was kept in the range of 10.0-1 000 mg·L^-1, with detection limit (3S/N) of 0.010%. On the base of blank sample, test for recovery was made by standard addition method; values of recovery found were in the range of 101%-106%, with RSDs (n=6) of recovery amounts in the range of 1.5%-7.2%.