The objective of this paper is to establish the high performance liquid chromatog. to determine tranilast and its related substances in tranilast eye drops.The high performance liquid chromatog. was performed on Lichrospher C18 (200 mm × 4.6 mm, 5 μm) column.The mobile phase consisted of methanol and 0.02 mol/L-1 monobasic potassium phosphate buffer (60:40).The flow rate was 1.0 mL/min-1 and the detection wavelength was set at 333 nm.The results showed that the assay showed good linear correlation over the range of 25-200 mg/L-1 (r = 0.999 9).The average recovery was 98.86% with the relative standard deviation = 1.10% (n = 9).The concentrations of tranilast in tranilast eye drops was 99.57%, 100.17%, 99.87% and the related compound in tranilast eye drops was 0.52%, 0.56%, 0.55% resp.It was concluded that the high performance liquid chromatog. is accurate, sensitive and repeatable with valuable application to the quality control of tranilast eye drops.