Aerogel　fiber　has　emerged　recently　for　incorporation　in　personal　thermal　management　textiles　due　to　its　flexibility,　scalability,　and　ultrahigh　porosity,　which　allows　the　body　to　keep　warm　via　thermal　isolation　without　energy　consumption.　However,　the　functionalization　and　intellectualization　of　cellulose-based　aerogel　fibers　have　not　yet　been　fully　developed.　Herein,　we　propose　a　biomimicking　design　inspired　by　polar　bear　and　Siamese　cat　hair　that　combines　porous　cellulose　aerogel　fiber　(CAF)　with　reversible　thermochromic　microcapsules　to　mimic　biological　sensory　and　adaptive　thermoregulation　functions.　The　produced　CAF　has　a　controllable　pore　structure,　a　large　specific　surface　area　(230　m2/g),　and　excellent　mechanical　strength　(∼15　MPa).　Low-temperature　darkening　microcapsules　have　been　incorporated　into　the　robust　CAF　to　spontaneously　adjust　color　by　perceiving　the　ambient　temperature.　The　functional　aerogel　fiber　fabric　achieves　high　thermal　insulation　and　photothermal　modulation　simultaneously　at　temperatures　below　18　°C.　The　temperature　of　the　thermochromic　fabric　was　higher　by　6　°C　than　that　of　the　sample　without　the　microcapsules　at　a　light　intensity　of　0.2　W/cm2.　In　addition,　the　aerogel　fibers　mixed　with　two　types　of　thermochromic　microcapsules　exhibit　three　color　switches　with　fast　response,　a　color-control　precision　of　0.2　°C,　and　good　cycling　performance.　This　smart　aerogel　fibers　hold　great　promise　for　self-adaptive　thermal　management,　temperature　indication,　information　transfer,　and　anticounterfeiting　in　textiles.　©　2023　American　Chemical　Society.