Abstract: Mechanical property analysis of backfill is an important basis for determining the reason‐ able backfill strength in underground mining of metal mines, which is directly related to the balance be‐ tween stope safety production and backfill economy and is of great significance to backfill mining in deep mines. A systematic study is carried out on the backfill prepared with a new cementing material in Zhang‐ zhuang Iron Mine. The micrograph of mine tailings is obtained by scanning electron microscopy, and the particle size distribution is analyzed with ImageJ software. Unclassified tailings backfill specimens with ce‐ ment-sand ratios of 1∶4, 1∶8 and 1∶15 are prepared, and uniaxial and conventional triaxial compression tests are conducted under standard curing conditions. The mechanical response and failure characteristics of backfill are systematically investigated. Test results reveal that the backfill exhibits a tensile failure mode dominated by vertical crack propagation. The post-peak stress strengthening characteristic and plas‐ tic deformation capacity of specimens are found to be more significant under the conditions of a lower ce‐ ment-sand ratio and a higher confining pressure. Meanwhile, the uniaxial compressive strength, elastic modulus and cohesion of backfill specimens increase linearly with the cement-sand ratio. Based on test da‐ ta, calculation formulas for mechanical parameters of backfill considering the variation of cement-sand ra‐ tio are proposed through fitting, and good fitting performance is achieved. The research results provide sci‐ entific support for the safety backfill design and backfill strength optimization in Zhangzhuang Iron Mine, and offer an important reference for balancing the mining safety and economic benefits of the mine.