Abstract: A method was developed with high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry(HPLC-MS/MS) for simultaneous detection of praziquantel residues in milk products. The praziquantel residues were extracted with acetonitrile-dichloromethane or ethylacetate, separated by C₈ column and analyzed using HPLC-MS/MS in positive mode. Extraction solvent and matrix effects of the praziquantel were discussed. The average recoveries are 81.8%-108.2% with the relative standard deviations of 2.6%-12.7%.