The fluidity and strength of cemented tailings backfill materials are 2 of the most critical performanceindicators that determine the quality and effectiveness of backfilling. This study investigates the effects of incorporatingcompound additives that are mainly liquid sodium silicate and water reducers on improving the fluidity and strength ofcemented ungraded tailings backfill materials at the Erdaogou Gold Mine. The results show a clear nonlinear relationshipbetween slump and slurry concentration: the higher the slurry concentration, the greater the decrease in fluidity causedby further increases in concentration. Compound additives can significantly enhance the fluidity of ungraded tailingsbackfill slurry, with their effects becoming more pronounced as slurry concentration and cement⁃sand ratio increase.The cement⁃sand ratio and curing age have a significant influence on the strength improvement effect of compoundadditives, whereas the influence of slurry concentration is negligible. There is a coupling effect between the cementsandratio and curing age on the strength enhancement of compound additives. In practical production, the use of additives toimprove the backfill strength can significantly reduce cement consumption and lower backfilling costs.