Per-　and　polyfluoroalkyl　substances　(PFAS)　are　emerging　contaminants　with　widespread　usage　and　remarkable　environmental　stability.　The　available　optical　sensing　methods　typically　exploit　the　hydrophobic　and　oleophobic　properties　of　PFAS　to　induce　the　aggregation　of　other　substances　and　achieve　indirect　detection　of　PFAS.　In　this　paper,　we　directly　measure　the　surface-enhanced　Raman　scattering　(SERS)　spectra　of　PFAS　themselves　based　on　microstructured　optical　fibers　decorated　with　β-cyclodextrin　and　silver　nanoparticles.　β-cyclodextrin　forms　host-guest　complexes　with　PFAS,　accessing　the　hot　spots　of　silver　nanoparticles.　Simultaneously,　the　microfluidic　channels　and　light　waveguide　within　the　microstructured　optical　fibers　greatly　extend　the　interaction　length　between　the　excitation　laser　light　and　PFAS.　This　platform　enables　rapid　and　sensitive　PFAS　sensing　with　characteristic　peaks　emerging　upon　liquid　introduction　into　the　optical　fibers　and　a　detection　limit　as　low　as　40　ng/L　for　perfluorooctanoic　acid.　Furthermore,　the　effective　differentiation　of　PFAS　with　similar　structures　but　different　C-F　chain　lengths　and　terminal　functional　groups　is　realized　by　combining　SERS　detection　with　principal　component　analysis　(PCA).　©　2024　American　Chemical　Society.