Calcium　salt　is　an　important　contributing　factor　for　calcium-based　biomineralization.　To　study　the　effect　of　calcium　salt　on　soil　biomineralization　using　crude　soybean　urease,　the　calcium　salts,　including　the　calcium　chloride　(CaCl2),　calcium　acetate　((CH3COO)2Ca)　and　calcium　nitrate　(Ca(NO3)2),　were　used　to　prepare　the　biotreatment　solution　to　carry　out　the　biomineralization　tests　in　this　paper.　Two　series　of　biomineralization　tests　in　solution　and　sand　column,　respectively,　were　conducted.　Scanning　electron　microscopy　(SEM)　and　X-ray　diffraction　(XRD)　were　performed　to　determine　the　microscopic　characteristics　of　the　precipitated　calcium　carbonate　(CaCO3)　crystals.　The　experimental　results　indicate　that　the　biomineralization　effect　is　the　best　for　the　CaCl2　case,　followed　by　(CH3COO)2Ca,　and　worst　for　Ca(NO3)2　under　the　test　conditions　of　this　study　(i.e.　1　mol/L　of　calcium　salt-urea).　The　mechanism　for　the　effect　of　the　calcium　salt　on　the　biomineralization　of　crude　soybean　urease　mainly　involves:　(1)　inhibition　of　urease　activity,　and　(2)　influence　on　the　crystal　size　and　morphology　of　CaCO3.　Besides　Ca2+,　the　anions　in　solution　can　inhibit　the　activity　of　crude　soybean　urease,　and　NO3−　has　a　stronger　inhibitory　effect　on　the　urease　activity　compared　with　both　CH3COO−　and　Cl−.　The　co-inhibition　of　Ca2+　and　NO3−　on　the　activity　of　urease　is　the　key　reason　for　the　worst　biomineralization　of　the　Ca(NO3)2　case　in　this　study.　The　difference　in　biomineralization　between　the　CaCl2　and　(CH3COO)2Ca　cases　is　strongly　correlated　with　the　crystal　morphology　of　the　precipitated　CaCO3.　©　2024　Institute　of　Rock　and　Soil　Mechanics,　Chinese　Academy　of　Sciences