Abstract: In order to accurately and rapidly determine BaP content in mainstream cigarette smoke, a liquid chromatography-atmospheric pressure photoionization-tandem mass spectrometry (LC-APPI-MS/MS) for determination BaP in mainstream cigarette smoke was developed and validated. The flow rate of toluene, extraction solvent, number of cigarette and the conditions of liquid chromatography and mass spectrometry were optimized. The results indicated that when the flow rate of toluene was 80 µL/min, cyclohexane was used as extraction solvent, chromatographic separation was achieved by using an Agilent PAH column (100 mm×2.1 mm, 3.5 μm) at 40℃, and 95% acetonitrile and 5% water was selected as the mobile phase, the detection limit of the method was 0.15 ng/mL, the recovery of BaP was 100%-107%, the relative standard deviation was less than 10%, and the analysis time was 6 min. Compared with the existing GC-MS method for the determination of BaP in mainstream cigarette smoke, this method shortened the analysis time. The proposed method has the advantages of high sensitivity and short analysis time etc., which can significantly improve the throughput.