Abstract: Cyanide tailings can be used as backfill aggregate for underground filling, but cyanide tailings contain highly toxic cyanide, which requires deep decyanation treatment. As a green, low-carbon and low-cost method, microbial treatment has broad application prospects. In this study, the cyanidation tailings slurry produced by a gold mine enterprise was selected to carry out the experimental study on the microbial deep treatment of cyanidation tailings slurry, and the effects of key factors such as slurry concentration, inoculation amount and nutrients on the microbial decyanation effect under the cyanidation tailings slurry system were investigated. The results showed that under the conditions of inoculation of 10 % CG301, glucose dosage of 1.5 g/L, reaction temperature of 30 °C, stirring speed of 300 rpm, aeration rate of 0.10 L/(min·L) and pH=9.5 in the slurry system with 30 % pulp concentration, the concentration of CN_f in the leaching solution of filter residue decreased to 0.020 mg/L after 24 h of microbial treatment, which met the technical requirements of backfill disposal of cyanide residue in "Technical Specification for Pollution Control of Cyanide Residue in Gold Industry". This study provides a reference for the green deep treatment of cyanide tailings slurry by microbial method.