To　improve　the　mechanical　properties　of　calcareous　sand,　it　is　proposed　that　microbial　induced　calcium　carbonate　precipitation　(MICP)　technology　be　used.　A　series　of　solidification　tests　were　conducted　in　natural　seawater　and　freshwater　environments.　The　standard　stress　path　static　triaxial　apparatus　was　used　to　conduct　shear　tests　on　calcareous　sand　and　solids　under　varying　reinforcement　conditions.　The　composite　power-exponential　(CPE)　model　is　proposed　to　describe　the　stress-strain　relationship　curve　of　the　solid,　and　the　method　for　determining　model　parameters　is　presented.　The　experimental　results　showed　that　the　strength　of　calcareous　sand　with　solids　increased　with　the　increase　in　number　of　reinforcement　times　for　both　test　environments.　Owing　to　the　high　salinity　of　seawater,　which　inhibits　the　activity　of　urease　in　bacterial　solutions,　the　reinforcement　strength　in　the　seawater　environment　was　generally　lower　than　that　in　the　freshwater　environment.　The　compactness　had　an　evident　effect　on　the　strength　of　the　added　solids.　With　the　increase　in　compactness,　the　strength　of　the　sample　also　increased,　but　the　rate　of　increase　was　reduced.　The　simulation　results　showed　that　the　established　constitutive　model　can　accurately　describe　the　stress-strain　relationship　of　microbial-reinforced　calcareous　sand　and　verified　the　applicability　of　the　model.