Background and aims <p>Soil heavy metal pollution around tailings in arid and semi-arid regions may pose a greater threat to the ecological environment, especially caused by cadmium (Cd). It is urgent to develop in-situ passivation remediation technology. This research assessed the efficiency of the integration of biochar application and artificial cyanobacteria inoculation for the immobilization of Cd²⁺.</p> Methods <p>Through soil incubation experiments, the effects of cyanobacterial biocrust-biochar on soil physicochemical properties, the bioavailability and fractions of Cd²⁺, the fluorescence characteristics of extracellular polymeric substances (EPS), the microbial community composition and Cd resistance gene abundance were systematically analyzed.</p> Results <p>After 45 d of inoculation, cyanobacteria biocrust-biochar not only increased soil pH, cation exchange capacity (CEC), organic carbon (OC), available nitrogen (AN), EPS content and the abundance of Cd resistance-related genes, but also effectively reduced Cd²⁺ bioavailability and migration efficiency. The proportion of acid-soluble Cd in the soil decreased by 24.92%, whereas the residual Cd fraction increased by 42.68% compared to the control (CK). The combined application of the two amendments achieved the highest efficiency in immobilizing Cd²⁺. Cyanobacteria biocrust-biochar can immobilize Cd²⁺ in soil by regulating EPS secretion, promoting Cd-resistant gene expression, and improving soil physicochemical properties, thereby achieving synergistic Cd²⁺ stabilization.</p> Conclusions <p>These findings demonstrate that the combination of biochar amendment and cyanobacteria inoculation technology shows great potential as a passivation approach for remediating soil contaminated with Cd.</p>