Abstract: The activity of the silicon-rich iron tailings powder under different curing conditions and its enhancement effect in concrete are characterized by introducing the concept of activity indicators，the strength contribution value and the strength contribution rate etc.. The results show that mechanical grinding can hardly change the activity of powder of iron tailings while curing conditions go to the opposite. Moreover，the powder of iron tailings does not own the pozzolanic activity under standard curing，90 ℃ hot water curing and 200 ℃ high-temperature curing，and its enhancement effect on concrete mainly belongs to micro-aggregate filling effect. Under autoclave curing conditions，powder of iron tailings have a obvious reactivity，and greatly inhance the strengthen of the concrete. With the specific surface area of 751 m²/kg，and the mixing amount of 20%,powder of iron tailings own the strength contribution rate of 23.5%，27.3%，30.9% at 3 d，28 d,56 d respectively. According to the different curing conditions，the specific surface area is appropriate to be 500 ~ 750 m²/kg and the amount of substitute of cement will be 20%.

Key words: Silicon-rich iron tailings powder, Reactive activity, Curing conditions, Enhancement effect