Abstract: A method based on liquid chromatography tandem mass spectrometry(LC-MS/MS) was developed for simultaneously determining the residues of 15 organophosphorus pesticides in tobacco.The samples were extracted with 50%(v/v) acetonitrile water solution,the extracts were cleaned up with primary secondary amine(PSA) adsorbent and magnesium sulfate,then filtrated by 0.45 μm filter membrane,and analyzed by LC-MS/MS with multiple reaction monitoring(MRM) mode,using water containing 0.05% acetic acid and methanol as a mobile phase at the flow rate of 1 mL/minute.The limits of detection and the recoveries of the organophosphorous pesticides were 2.58 to 11.5 μg/kg and 66% to 104%,respectively,with RSDs of below 8.99%.