Microbial-induced carbonate precipitation (MICP) has been widely used in the remediation of heavy metal contaminated soil. Two urease-producing bacteria, Octococcus pasteurii and Bacillus cereus , with or without exogenous Ca²⁺ were introduced to Cd-As co-contaminated paddy soil in order to optimize the process of MICP and improve remediation efficiency. The impact of exogenous CaCl₂ on the efficacy of Cd and As remediation in the soil under two strains treatments, as well as the changes of soil properties, enzyme activities and microbial diversity after remediation were studied. Results showed that two strains were able to immobilize Cd and As in soil, compared with Octococcus pasteurii, Bacillus cereus reduced available Cd and As contents by 16.7% and 11.1%, respectively. The addition of exogenous Ca²⁺ reduced available Cd and As by 17.3%–22.2% and 16.8%–26.7% in both bacterial treatments, respectively, indicating that the addition of Ca²⁺ accelerated MICP process and immobilized Cd and As. Compared with the treatment without Ca²⁺, the addition of Ca²⁺ significantly increased soil urease (52.6%–113.3%), sucrase activity (13.1%–28.9%), alkaline hydrolysis nitrogen (3.4%–25.5%), available potassium (2.1%–34.1%) and microbial diversities in both bacterial treated soils, implying that the addition of exogenous Ca²⁺ effectively enhanced soil fertility and soil ecological functions. In conclusion, the remediation efficiency of Cd-As co-contaminated soil by urease producing bacteria can be improved by the addition of Ca²⁺, with Bacillus cereus offering a higher efficiency for reducing the phytoavailability of heavy metals in soil.