Abstract: A method for simultaneously determining the benzoapyrene(BaP) and 4-(N-methyl-Nnitrosamino)-1-(3-pyridyl)-1-butanone(NNK) in mainstream cigarette smoke by gas chromatography-tandem mass spectrometry(GC-MS/MS) was developed.The total particulate matter of mainstream cigarette smoke was collected on a Cambridge filter pad,then extracted with toluene by oscillation.The extract was cleaned up by dispersive solid phase extraction(d-SPE),concentrated by nitrogen gas flow,separated by DB-35MS column,and determined by internal standard method under multi-reaction monitoring(MRM) mode.The results showed that:1) The limits of quantitations(LOQs),recoveries and relative standard deviations(RSDs) of NNK and BaP were 0.36 and 0.29 ng/cig,78.8%-95.5% and 101.6%-106.6%,2.3%-15.4% and 2.9%-14.4%,respectively.2) Comparing with the standard method,the developed method was simpler in pretreatment,and capable of simultaneous determination of the two target analytes.3) The data of 27 cigarette samples determined by the developed method well agreed with those by the standard method,there was no significant difference.The method is simple,accurate and suitable for the simultaneous determination of NNK and BaP in mainstream cigarette smoke.