Sartans and related analogues with 5-oxo-l, 2, 4-oxadiazole ring and tetrazole ring are investigated in detail using collision-induced dissociation (CID) method in positive ion mode by electrospray ionization tandem mass spectrometry (ESI-MSn ). It is found that the protonated sartans and related analogues tend to form the N-substituted-3-substituted phenanthridin-6-amine ion which has a large conjugative structure. The possible fragmentation pathways were proposed for the first time, and the key structure of product ions was confirmed by high resolution tandem mass spectrometry and theoretical calculation. It is very helpful for understanding the intriguing roles of sartans analogues in fragmentation reactions and enriching the knowledge of the gas-phase chemistry of the oxadiazole and tetrazole ring. Copyright © 2017 John Wiley & Sons, Ltd.