Abstract: The fragmentation characteristics of two typical cyclic imine toxins (GYM and SPX1) were analyzed by ion trap-atmospheric pressure chemical ionization-mass spectrometry (IT-APCI-MS). The results showed that quasi-molecular ion peakM+H⁺ (base peak) of GYM and SPX1 was detected by APCI-MS. Stability characteristic fragment ions were observed by the neutral loss of H₂O from precursor ions M+H⁺ for APCI-MS². Then, the fragmentation pathways of GYM and SPX1 were discussed based on APCI-MS³ analysis. Based on the comparison of two methods, the sensitivity of APCI-MS is better than ESI-MS for analysis of GYM and SPX1. The matrix interference resistance, specificity, repeatability and stability of the LC-APCI-MS² method are better than LC-ESI-MS² method for analysis of GYM and SPX1 in four different matix. In conclusion, APCI-MS is suitable for determination of cyclic imine toxins, and this study can provide a good reference and basis for qualitative and quantitative analysis of cyclic imine toxins in different complex matrix samples by LC-APCI-MS.