Lithium-sulfur　(Li-S)　batteries　have　attracted　great　interest　for　next-generation　batteries　owing　to　their　high　capacity　density　and　low　cost.　However,　the　drawbacks　of　the　low　conductivity　of　sulfur,　serious　＂shuttle　effect＂　and　huge　volume　expansion　during　the　charging/discharging　cycles　greatly　limit　their　practical　applications.　In　this　work,　we　report　the　synthesis　of　porous　sulfurized　poly(acrylonitrile)　(PAN/S)　nanofibers　via　thermal　treatment　of　PAN/poly(methyl　methacrylate)　(PMMA)　nanofibers　with　elemental　sulfur,　resulting　in　48　wt%　of　covalently　bound　sulfur　formed　in　the　composite.　The　unique　porous　structure　of　nanofibers　enables　enhanced　diffusion　dynamics　of　ions　and　electrons,　thus　improving　the　reactivity　and　conductivity　of　sulfur.　As　a　consequence,　the　porous　PAN/S　cathode　delivers　a　high　reversible　capacity　of　1144　mA　h　g(-1)　after　100　cycles　at　a　current　rate　of　0.2　C　and　a　high　rate　performance　with　a　reversible　discharge　capacity　of　794　mA　h　g(-1)　at　2　C　after　500　cycles.　(C)　2020　Elsevier　B.V.　All　rights　reserved.