Localized　surface　plasmon　resonance　(LSPR)　biosensors　find　widespread　applications　in　biomedical　engineering,　environmental　monitoring,　and　food　safety　owing　to　their　nondestructive　and　rapid　detection　capabilities.　However,　the　sensitivity　of　LSPR　sensors　is　constrained　by　their　broad　spectral　response.　This　study　introduces　a　tunable　Fano　resonance　biosensor　that　leverages　the　coupling　of　LSPR　and　Rayleigh　anomaly　(RA).　The　refractive　index　sensitivity　of　the　sensor　was　evaluated　through　measurements　of　glucose/water　solutions　at　various　concentrations,　demonstrating　a　refractive　index　sensitivity　of　685　nm/RIU.　Furthermore,　the　sensor　chip　functionalized　with　IgG　antibodies,　enables　label-free　detection　of　IgG　antigens　and　real-time　monitoring　of　biological　reaction　dynamics.　The　sensor　chip　exhibits　a　detection　limit　of　40　ng/mL.　This　straightforward　and　highly　sensitive　biosensor　chip　holds　promise　for　applications　in　immunoassays,　clinical　diagnostics,　and　drug　screening　in　the　future.