Biopolymers　and　the　enzyme-induced　calcite　precipitation　(EICP)　technology　have　been　widely　studied　and　applied　in　soil　improvement.　They　each　possess　unique　characteristics　and　different　mechanisms　of　action,　yet　there　is　currently　still　a　lack　of　in-depth　understanding　of　their　combined　effect.　Therefore,　this　paper　utilized　the　combination　of　EICP　with　two　types　of　biopolymers,　namely,　sodium　alginate　and　guar　gum,　to　reinforce　Chinese　standard　sand.　A　series　of　physical,　mechanical,　and　microscopic　tests　were　conducted　on　the　sand　treated　by　EICP　combined　with　different　biopolymer　contents.　The　test　results　show　that　EICP　combined　with　biopolymer　treatment　can　enhance　the　strength　and　impermeability　of　sand　more　evidently,　and　the　sodium　alginate　exhibits　a　better　effect　than　guar　gum.　The　guar　gum　increases　the　viscosity　of　the　reaction　solution,　hindering　the　migration　of　ions　within　it　and　leading　to　a　rise　in　local　ion　concentration,　which　promotes　the　deposition　of　calcium　carbonate.　In　contrast,　sodium　alginate　formed　a　gel　network　between　sand　particles　through　ion　exchange,　inhibiting　the　deposition　of　calcium　carbonate.　EICP　combined　with　sodium　alginate/guar　gum　treatment　can　greatly　reduce　the　proportion　of　large　pores　in　sand,　thus　improving　its　pore　structure.　The　findings　of　this　study　confirm　the　superiority　of　EICP　combined　with　biopolymer,　which　is　expected　to　provide　a　reference　for　subsequent　research　and　practical　geotechnical　engineering　applications.　©　2025　American　Society　of　Civil　Engineers.