The reductive degradation of technical perfluorooctanesulfonate (PFOS) were investigated in a biomimetic system consisting of vitamin B₁₂(VB₁₂) as catalyst and nanoscale zero-valent iron (nFe⁰) as reductants. Both branched and linear PFOS could be degraded simultaneously, and the biomimetic degradation of linear PFOS was first reported. The degradation was well described by a pseudo-first-order kinetic model, and increasing the incubation temperature was favorable for the removal of PFOS and for its defluorination. Three types of PFOS degradation products, including 4 perfluoroalkylsulfonates (perfluorocarbon chain length:C4~C7), 9perfluorocarboxylates (perfluorocarbon chain length:C2~C7, C10, C11, and C13), and 5 polyfluorinated acids (i.e. H-perfluorohexanoate, H-perfluoroheptanoate, H-perfluorooctanoate, H₂-perfluorooctanoate, and H-perfluorooctanesulfonate) have been qualitatively determined by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF). For the first time, Perfluoroalkylsulfonates and perfluorocarboxylates were detected among the biomimetic reduction products of PFOS catalyzed by VB₁₂, while some long-chain perfluorocarboxylates, including perfluoroundecanoate (C10), perfluorodocecanoate (C11) and perfluorotetradecanoate (C13), were first reported as the degradation products during decomposition of PFOS. It was unclear whether H-perfluoroalkanes (carbon chain length:C2~C7, C10, C11, and C13) were the biomimetic degradation products of PFOS, and further investigation is warranted.