Abstract: In order to investigate the impacts of tailings powder substitution for cement on the mechanical properties of low-strength concrete, this work replaced 0～30% of cement by mass with tailings powder. Its effects on the setting time and mechanical properties of C25 concrete, and characterized the hydration products and microstructure of hardened paste was analyzed using scanning electron microscopy（SEM） and X-ray diffraction（XRD）. The results indicate that gold tailings powder, as an auxiliary cementitious material, can prolong the setting time of C25 concrete. Within the range of 30% gold tailings powder substitution, both slump and setting time meet the requirements of ordinary Portland cement standards. The compressive strength, axial compressive strength, and static modulus of elasticity of C25 concrete show a trend of initially increasing and then decreasing with increasing gold tailings powder content, with a peak observed at a substitution rate of 5%. SEM and XRD analyses reveal that with increasing curing age, the surface of gold tailings powder particles is covered by hydration products, resulting in fewer and more tightly packed pores, exhibiting favorable mechanical properties. However, as the substitution rate of gold tailings powder increases, the hydration products exhibit a looser microstructure, leading to a decrease in mechanical performance.