Abstract: In order to study the effect of different proportion of iron tailings powder on workability， mechanical property and microscopic mechanism of dry mortar，experiments of iron tailings powder were used as the research object to replace the machine-made sand and cement. The results show that the mechanical property of dry-mixed mortar was decreased with the increase of iron tailings powder when the total amount of powder material and machine-made sand remain the same. When the iron tailings powder was used to replace the machine-made sand with 10%，the performance of M20-mortar was the best and met the requirement of workability and mechanical property. When the replacement rate of iron tailings powder to machine-made sand reaches 30%，the workability and mechanical property of M5-mortar can be met. The incorporation of iron tailings powder can accelerate the hydration of cement，increase the degree of hy⁃ dration，and generate more Ca（OH）₂ at early age. The silicon-oxygen break bond and aluminum-oxygen break bond in iron tailings powder can reunite under the action of Ca（OH）₂ and form the double-salt minerals with calcium silicate and calcium silico-aluminate. The mortar’s structure was loose when the iron tailings powder was added，so its compressive strength was decreased. Dry-mixed mortar can meet the stan⁃ dard of specification requirement when 10% to 30% mechanical sand and cement were replaced by iron tailings powder.

Key words: iron tailings powder, dry mortar, workability, strength, microscopic mechanism