The fragmentation mechanisms of pyridine compounds in extractive atmospheric pressure chemical ionization mass spectrometry（EAPCI-MS） analysis were investigated.The experiments showed that under the ambient conditions，the protonated molecular ion peak［M+H］+ and molecular ion peak M+? could be simultaneously observed using the EAPCI-MS,and similar fragmentation rules can be obtained for their collision induced dissociation（CID） ，without any sample pretreatment and supporting reagent.It is obvious that,compared with that of the traditional ion sources，the chemical selectivity and qualitative analysis of EAPCI source are significantly improved for the rapid detection of pyridine compounds，in which the EAPCI source has both the fragment characteristics of traditional ion sources of ESI and APCI.This study provided a novel method for the qualitative detection of pyridine compounds.