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One important pathway for human exposure to per- and polyfluorinated alkyl substances (PFASs) is based on the Earth's atmosphere. Figuring out atmospheric transformation mechanism of PFASs is beneficial for understanding their effects on humans. However, the focus on the molecular-level transformation mechanism of emerging PFASs in the atmosphere still need to be improved. In this work, we used quantum chemistry calculation to study ·OH-initiated degradation mechanism of a new fluorinated alcohol (C 3 F 7 OCHFCF 2 SCH 2 CH 2 OH, abbreviated FESOH) in the presence of oxygen and nitric oxide. Three main conformers of FESOH share the similar initial mechanism that the abstraction reactions of H atom at α-C and β-C atoms are the main pathways (activation free energies of <10 kcal mol−1 at 298 K), but make different contributions to the whole FESOH degradation. Subsequent transformations starting from initial products at α-C atoms will reunite with that at β-C atoms, and the intermediate (C 3 F 7 OCHFCF 2 S·) is produced. After O 2 addition to the intermediate and the following SO 2 elimination, the alkyl radical (C 3 F 7 OCHFCF 2 ·) can undergo consecutive chain cleavage cycles to form CF 3 OH finally. The bioaccumulation evaluation shows that FESOH and its transformation products cannot be accumulated in organisms. The work is helpful for knowing the atmospheric fate of FESOH at molecular level and can provide some insight into the transformation of other PFASs in the atmosphere. [Display omitted] • Three main conformers of FESOH account for approximate 99% of all conformers. • The H-abstraction at α-C and β-C mainly occurs for ·OH-initiated FESOH degradation. • Subsequent reactions can form alkyl peroxynitrite, fluorinated aldehyde and CF 3 OH. • FESOH and its transformation products cannot be accumulated in organisms. [ABSTRACT FROM AUTHOR]