A gas chromatography-flame ionization/tandem mass spectrometry detection method for alkaloids in cigarette side stream smoke is characterized in that the method comprises that a Cambridge filter is mounted in a side stream smoke smoking machine, the cigarette side stream smoke alkaloids are captured, after a NaOH aqueous solution is added, dichloromethane is used for extraction, and an organic solvent layer is taken for analysis; and a sample is separated by a chromatographic column and then enters a flame ionization detector (FID) and a tandem mass spectrometer (MS-MS) for determination, and thus accurate qualitation and quantitation of the cigarette side stream smoke alkaloids is achieved. The gas chromatography-flame ionization/tandem mass spectrometry detection method is applied in determination of the cigarette side stream smoke alkaloids with large content difference and complex sample matrix for the first time; the method has simple pretreatment, the to-be-tested sample only needs one-needle sample injection, and FID accurate quantitative analysis of nicotine and MS-MS accurate quantitative analysis of secondary alkaloids can be met. The method has the advantages of simple pretreatment, high sample determination and analysis efficiency, good repeatability and high recovery rate, and is suitable for batch analysis of samples.