A simple, selective, and sensitive method using hydrophilic interaction chromatography combined with tandem mass spectrometry (HILIC-MS/MS) for quantifying perchlorate in milk powder and milk was developed. The analysis was conducted on an Inertsil HILIC column (150 mm x 3.0 mm, 3.5 mum) using a mobile phase consisting of methanol and 0.1% formic acid (60:40, v/v). The detection was performed by MS/MS via electrospray ionization. Linear calibration curves were obtained in the concentration range of 2.00 x 10(-2) to 8.00 microg/g and 4.00 x 10(-1) to 20.0 microg/L for perchlorate in milk powder and milk, respectively. The method detection limit was 4.00 x 10(-3) microg/g for milk powder and 8.00 x 10(-2) microg/L for milk. The recoveries of perchlorate in milk powder and milk were all >90%. This method was successfully applied to the quantitative determination of perchlorate in milk powder and milk.