AISI　321　stainless　steel　is　widely　used　in　hydrogenation　refining　pipes　and　hydrogen　storage　vessel　and　so　on　owing　to　its　excellent　performance　of　creep　stress　resistance　and　high-temperature　resistance.　In　this　study,　slow　strain　rate　tensile　tests　(SSRT)　were　conducted　under　the　condition　of　electrolytic　hydrogen　charging　(EHC).　The　hydrogen　embrittlement　mechanism　of　AISI　321　stainless　steel　was　analyzed　in　detail　by　means　of　scanning　electron　microscopy(SEM),　X-ray　diffraction　spectrometer　(XRD)　and　transmission　electron　microscope　(TEM).　The　results　show　that　hydrogen　can　change　the　fracture　mode　of　tensile　specimens　from　ductile　fracture　to　brittle　fracture　mode.　The　main　reason　is　that　dislocations　slide　carrying　hydrogen　continuously　in　the　material　under　the　action　of　slow　strain　rate　stress,　resulting　hydrogen　cracks　are　preferentially　produced　at　austenite　grain　boundaries,　inclusions　and　the　interface　between　δ　ferrite　and　austenite.　Additionally,　it　is　easy　to　induce　the　transformation　and　growth　of　α＇　martensite　in　the　process　of　hydrogen　charging　and　reduce　the　plasticity　of　the　material.　©　2021　Elsevier　Ltd