Shrinkage　cracks　present　significant　challenges　to　the　long-term　performance　of　concrete　structures.　These　issues　can　be　effectively　mitigated　by　incorporating　various　fiber　types　that　provide　anchorage　and　bridging　effects　between　the　fibers　and　cement　matrix　composites.　Research　has　shown　that　cellulose　fibers　(CFs)　can　significantly　reduce　shrinkage　and　enhance　the　mechanical　performance　of　cement-based　materials.　Herein,　the　effects　of　CF　on　the　shrinkage,　anticrack　performance,　mechanical　properties　of　concrete,　and　its　mechanism,　are　investigated.　First,　three-point　bending,　uniaxial　compression,　and　shrinkage　tests　for　the　mortar　were　conducted　using　three　types　of　millimeter-scale　CF　(CF960,　CF850,　and　CF800)　at　different　concrete　contents　(0.6,　0.9,　1.2,　1.5,　and　1.8　kg/m3　of　concrete).　The　optimal　fiber　category　and　CF　content　range　were　selected　based　on　the　mechanical　and　shrinkage　properties　of　the　mortar　using　the　entropy　weight-TOPSIS　method.　Then,　four-point　bending,　uniaxial　compression,　uniaxial　splitting,　and　three-point　fracture　tests　were　performed　on　specimens　at　different　CF　contents　(0.6,　0.9,　1.2,　and　1.5　kg/m3)　to　assess　the　mechanical　and　fracture　properties.　To　evaluate　the　shrinkage　caused　by　self-desiccation,　cement　hydration,　and　environmental　temperature　changes,　drying,　autogenous,　and　temperature　shrinkage　tests　were　conducted.　A　prediction　model　for　the　drying　and　autogenous　shrinkage　properties　was　developed　based　on　the　grey　prediction　model　GM　(1,1).　Crack　width,　length,　and　area　were　selected　to　evaluate　plastic　shrinkage　performance.　Finally,　microscopic　analyses　of　different　CF　contents　were　conducted　using　scanning　electron　microscopy　and　mercury　intrusion　porosimetry.　The　experimental　results　revealed　that　CF　refined　the　pore　structure　of　concrete　and　exerted　a　bridging　effect,　thereby　enhancing　the　mechanical　and　fracture　toughness　performance　of　concrete.　The　optimal　type　and　content　of　CF　for　concrete　are　CF960　at　1.2　kg/m3.　The　lumen　structure　of　the　CF　improves　the　cement　hydration　process　and　the　effect　of　retaining　and　releasing　water,　thereby　reducing　shrinkage.