Trace amounts of sulphion can threaten the performance and lifespan of proton exchange membrane fuel cells (PEMFCs). The fuel mainly originates from refinery hydrogen, in which methyl mercaptan (MeSH), ethyl mercaptan (EtSH), dimethyl sulfide (DMS) and ethyl sulfide (EMS) inevitably exist. Herein, their negative effects are investigated on PEMFC and rotating disk electrode (RDE) levels, and the poisoning mechanisms are revealed by structural characterizations and density functional theory (DFT) calculations. The result indicates that MeSH and EtSH are 1.6 times more threatening than H2S, therefore, it is essential to limit the content of MeSH and EtSH. Nevertheless, the poisoning effect of DMS and EMS is weak enough to be tolerated. Moreover, the findings that the occupation of top site on Pt (111) weakly affects the hydrogen oxidation reaction (HOR) would contribute to the design of new catalysts with stronger toxicity resistance. This work is significant for the durability improvement of PEMFCs. Display omitted •MeSH and EtSH are 1.6 times more threatening than H2S on PEMFC.•The effect of occupation of top site on Pt (111) on the hydrogen oxidation reaction (HOR) is very weakly.•The adsorption mechanisms of MeSH, EtSH, DMS and EMS on Pt/C catalysts are given.