The　existence　of　kaolinite　inside　the　granite　joints　reduces　the　direct　contact　between　the　jointed　rock　walls,　which　is　an　unfavorable　factor　for　the　stability　of　underground　engineering.　However,　there　are　limited　studies　addressing　kaolinite-filled　granite　joints　of　different　filling　degrees　(the　ratio　of　filling　thickness　t　to　the　maximum　fluctuation　height　a　of　the　joint　surface　(t/a))　even　to　this　day,　and　the　shear　failure　mechanisms　of　kaolinite-filled　joints　remain　unclear.　Direct　shear　tests　of　kaolinite-filled　joints　with　different　filling　degrees　are　carried　out　in　this　study,　and　the　acoustic　emission　(AE)　activities　during　the　shearing　are　real-timely　monitored.　The　results　show　that　the　filling　degree　has　a　significant　influence　on　the　shear　properties　and　AE　characteristics　of　kaolinite-filled　joints.　With　the　increase　of　the　filling　degree,　the　shear　stress　drop　is　less　significant,　and　the　normal　deformation　gradually　transitions　from　＇first　shear　contraction　and　then　shear　dilation＇　to　＇shear　contraction＇,　which　is　accompanied　by　the　weakening　of　AE　signals.　The　increase　in　filling　degree　allows　a　transition　of　the　joint　behavior　from　the　asperity-dominated　damage　mode　to　the　kaolinite-dominated　shear　sliding　mode.　Moreover,　the　filling　degree　is　correlated　with　the　joint　roughness　coefficient　(JRC)　in　the　form　of　an　exponential　function　to　modify　Barton’s　shear　strength　criterion.　The　present　study　gets　insights　into　the　shear　failure　mechanisms　of　kaolinite-filled　joints　with　various　filling　degrees　and　helps　interpret　the　field　observations.　©　Korean　Society　of　Civil　Engineers　2024.