An HPLC method was developed for the determination of trichloroacetic acid in urine based on the interface reaction between trichloroacetic acid and pyridine.An orthogonal experiment was carried out and the result showed that there was no significant correlation among the factors.The derivatization conditions such as the volume of urine and reagent,alkali concentration,reaction time and temperature,and the chromatographic conditions were optimized.Under the optimal conditions,the working curves of the analyte was established,the linear range of trichloroacetic acid was between 0.002 0 mg/L and 20.0 mg/L,with correlation coefficient（r） of 0.999 7 and detection limit（S/N=3） of 0.1 μg/L.The average recoveries of trichloroacetic acid in urine samples were in the range of 91.9%-105% with relative standard deviations of 3.5%-4.6%.The results showed that the urine sample was simultaneously enriched and purified by using the interface reaction,and the detection limit was greatly reduced.The established method was turned out to be simple,rapid,sensitive,accurate and environment friendly.