Abstract: Two kinds of composite mineral admixtures were prepared by grinding iron tailings powder and silicon powder in the ratios of 3∶2 and 4∶1, respectively to substitute cement for the preparation of mortar and concrete samples. The basic properties of iron tailings-silica fume composite mineral admixture mortar and concrete have been studied through microstructure analysis, strength and durability analysis. Results show that: as the content of the composite mineral admixture increases, the heat of hydration reaction, compressive strength, split tensile strength and freeze-thaw durability of the sample gradually decrease; and adding iron tailings powder can increase the pore structure of the hardened mortar test block, which reduces the compressive strength and freeze-thaw durability of the concrete. However, increasing the amount of silica fume can increase the strength of the hydration reaction of the sample, and increasing the silica fume can reduce the content of Ca(OH)₂. The CSH gel produced by the hydration reaction of silica fume can also refine the pore structure, thereby improve the microscopic properties, compressive strength, split tensile strength and freeze-thaw durability of concrete; make up for the negative impact of iron tailings powder on concrete performance. On the whole, the compressive strength of modified concrete is more than 85% of that of ordinary concrete, which can meet engineering requirements.