The addition of ufitratine powder (UFP)to concrete can improve the fluidity of concrete, showing a water-reducing effect The aim of this article was to analyze the water-reducing mechanism of UFP both experimentally and theoretically. Three UFPs-fine ground slag. highcalcium fly ash, and low-calcium fly ash--weN chosen for the study. The contrastive experiments were done to investigate the fluidity of mortars with 30%, 45%, 60%. and 75% equivalent cement replaced by fine ground slag. high-calcium fly ash. and low-calcium fly ash. respectively. The results showed the physical and chemical characteristic of the powder, such as their grain morphology, glass phase activities, densities, specific areas, and their groin eumuhdng conditions, can strongly affect their water-reducing effect.