Abstract: The content of thiocyanate in liquid milk was determined by ion-pair RP-HPLC. The sample was extracted by acetonitrile, and the sample solution obtained was separated on Zorbax Extend C18 column (150 mm×4.6 mm, 5 μm) with a mixture of phosphate buffer solution (containing 3 mmol·L-1 tetrabutylammonium bromide) and methanol in the ratio 70 to 30 by volume as mobile phase, and detected at 231nm by UV-detector. Linear relationship between values of peak area and mass concentration of thiocyanate was kept in the range of 0.4-50.0 mg·L-1, with detection limit (3S/N) of 0.055 mg·L-1 and lower limit of determination (10S/N) of 0.18 mg·L-1. The proposed method was applied to the analysis of liquid milk. Tests for recovery and precision were made by standard addition method, giving values of recovery and RSD′s (n=6) in the ranges of 92.0%-102% and 2.53%-4.86% respectively.