Objective To establish a method for the determination of food additive theaflavins by ultraviolet spectrophotometry.Methods After dissolved in water， the sample solution was extracted with ethyl acetate and 2.5% sodium bicarbonate solution in turn. A certain volume of ester phase was fixed with ethanol， and then it was quantified by spectrophotometry. The maximum absorption wavelength， sample quality， concentration of sodium bicarbonate solution and extraction time by sodium bicarbonate solution were researched.Results Under the best conditions， four theaflavin monomers had good linear relationships within their respective concentration ranges， and the correlation coefficients were all greater than 0.999. The limit of quantitation was 3%， the standard recoveries were 95.2%-108.4%， and the relative standard deviations were less than 5%.Conclusion This method has good repeatability， precision and stability， and is suitable for the determination of food additive theaflavin.