Enzyme-induced　carbonate　precipitation　(EICP)　has　emerged　as　an　environment-friendly　solution　for　soil　improvement.　As　a　composite　material,　it　is　challenging　to　determine　the　micromechanical　properties　of　EICP-reinforced　sand　using　common　macromechanical　tests.　In　this　work,　a　systematic　study　was　conducted　to　determine　the　micromechanical　properties　of　EICP-reinforced　sand.　The　development　of　the　micromechanical　properties　obtained　from　indentations　along　the　route　of　＂sand　particle-CaCO3-sand　particle＂　was　examined.　The　width　of　the　interfacial　transition　zone　(ITZ)　in　EICP-reinforced　sand　was　investigated.　The　effect　of　the　reaction　environment　on　ductility　(i.e.,　the　ratio　of　elastic　modulus　over　hardness)　of　CaCO3　was　investigated.　The　experimental　results　have　identified　that　the　width　of　ITZ　in　EICP-reinforced　sand　ranges　from　0　to　180　mu　m,　which　is　significantly　influenced　by　the　crystal　crystallinity　or　crystal　morphology　of　CaCO3.　The　presence　of　porous　media　(i.e.,　sand　particles)　leads　to　the　decrease　in　impurity　content　in　the　crystal　formation　environment,　resulting　in　the　lower　ductility　of　CaCO3　accordingly.　The　mean　value　of　fracture　toughness　of　CaCO3　precipitation　was　identified　to　be　the　lowest　one　among　sand　particles,　CaCO3　precipitation,　and　sand　particles-CaCO3　interface.　The　lowest　fracture　toughness　of　CaCO3　indicating　the　failure　of　biocementation　is　derived　from　the　CaCO3-CaCO3　breakage.