Abstract: A headspace gas chromatography-mass spectrometry method was developed for determining phosphine residue in tobacco. The sample was injected after being oscillated at 40℃ in headspace sampler, then separated on GC Elite-624 capillary column (60 m×320 m×1.8 m), and finally determined by mass spectrometry monitoring ion fragment (m/z=34) under SIR mode. The results showed that:1) Good linearity was achieved when the content of PH3 ranged from 0.25-5.00 g/L. The detection limit, average recovery and relative standard deviation (RSD) (n=6) were 0.0019μg/g, 90.29% and 4.54%, respectively. 2) This method was simple, safe and accurate for determining phosphine residue in tobacco.