Abstract: The melamine in raw milk was extracted with acetonitrile, isolated by Biobasic SCX chromatographic column （250 mm× 150 mm, 5 μm） and detected by diode array UV-detector. The mobile phase was acetonitrile-0.05 mol/L potassium dihydrogen phosphate buffer solution （with volume ratio of 30：70） and the detection wavelength was 240 nm. In the addition concn, range of 5-20 mg/kg, the recovery of this method was 92 %-96 %, its RSD was smaller than 10 % and its detection limit was 0.25 mg/kg.