Objectives A high-performance liquid chromatography method was developed to determine the purity of theaflavins， a food additive.Methods The samples were dissolved in ethanol-water （2∶8，V/V） solution and separated by C₁₈ reversed-phase chromatography with acetonitrile and 0.1% phosphoric acid as mobile phase. The flow rate was 1 mL/min and the column temperature was 35 °C， the detection was performed at 278 nm using a UV detector.Results The linear relationship of theaflavins was good in the range of 20-500 μg/mL， and the correlation coefficient r²>0.99， the limit of detection of the four components of tea polyphenols was 0.2 μg/mL， and the limit of quantification was 0.5 μg/mL.The recovery rate of the samples was 97.9%-101.3%， and the relative standard deviation was 0.3%-1.6%.Conclusion The method has high precision， good stability， simple operation， and can meet the requirements for the purity determination of food additive theaflavin.