Abstract: A method was established for determining residue of pentachlorophenol in milk with gas chromatography(GC)-electron capture detector(ECD).The sample was extracted with acetone and derived with acetic anhydride.The derivative was determined by gas chromatography with electron capture detector.Good accuracy, precision and sensitivity were obtained with the method.The calibration curves of the derivative of pentachlorophenol were linear between the peak areas and the concentrations in the range of 5.00-500.00 μg/L with correlation coefficients(r²) of 0.999.The average recoveries of pentachlorophenol were 77.6%, 87.2% and 86.3% respectively at three spiked concentration of levels of 5,10 and 50 μg/kg, with relative standard deviations(RSDs) less than 9.6%.The limit of detection(LOD) for the derivative of pentachlorophenol was 2 μg/kg and the limit of quantitation(LOQ) was found to be 5 μg/kg. The study revealed that the method was suitable for the determination of pentachlomphenol in milk．