Abstract: The solidifying of Sr²⁺ by carbonate mineralization bacteria, Bacillus pasteurii, in an aqueous solution was investigated. CO₃^2- was produced by the enzyme digestion process of the species when urea was decomposing. Biochemical properties of urease from bacteria were involved in transforming free radioactive Sr²⁺ into stable SrCO₃. Various analysis and testing techniques, such as EDS, SEM, XRD and FT-IR, were used to analyse the precipitate. The experimental results showed that the microbiologically-induced SrCO₃ crystal particles have porous surface in chaotic sizes, bonding together forming irregular groups. Concentrations, cultivation time and urea concentrations of Sr²⁺ influenced the forming of SrCO₃ crystal morphology. It was also found that the bacteria participate in the progress of carbonate mineralization bacteria induced Sr²⁺ mineralization as nucleation sites. The solidifying rate reached a peak of 98.32% when the Sr²⁺ concentration was set as 0.05 mol/L, urea concentration was 30 g/L and pH was 8, cultivation was at 30 ℃ for 72 h, and therefore radionuclide stabilization treatment could be achieved.