The safe and effective application of ultra⁃fine gold tailings as backfill material holds significant envi⁃ronmental and economic importance. By using ultra⁃fine gold tailings produced by a gold ore processing plant as theprimary test material, a series of experiments was conducted to analyze the effects of different cementing agents,cement⁃to⁃sand ratios, and slurry concentrations on the mechanical properties of the backfill. Water quality changeswere also assessed through toxicity leaching tests. The research results indicate that the uniaxial compressive strength,bleeding rate, and settlement shrinkage rate of the backfill are significantly influenced by the cement⁃to⁃sand ratio, thetype of cementing agent, and the slurry concentration. As the cement⁃to⁃sand ratio decreases, the uniaxial compressivestrength decreases, while the use of a slag micropowder cementing agent and higher slurry concentrations help improvethe uniaxial compressive strength. The optimal process conditions are identified as a slag micropowder cementingagent, a cement⁃to⁃sand ratio of 1∶4, and a slurry concentration of 68 %. The bleeding rate and settlement shrinkagerate increase as the cement⁃to⁃sand ratio decreases, but increasing the slurry concentration can effectively reduce boththe bleeding rate and settlement shrinkage rate. Water quality testing results show that the water quality after backfillbleeding meets Class V standards, with most samples falling into Class Ⅱ-Ⅳ water quality, complying with nationalwastewater discharge standards and having a minor impact on underground water quality.