Abstract: In order to improve treatment effect of the slurry water, fly ash was applied to prepare the poly ferric silicate flocculant and an orthogonal test design was applied to study three major influence factors of n (Si) :n (AI) (quantity ratio of material) ,n(Si) :n (Fe) and curing temperature during the preparation process of the p oly ferric silicate flocculant.The results showed thatn(Si) :n(AI) =I.0:0.5, n(Si) :n (Fe) =1.0:0.5, the curing temperature of 60 °C and curing time of 2 h were the op timized technique conditions. The poly ferric silicate flocculant prepared was applied to the flocculation test of the slurry water.When the quality concentration of the slur ry water was 8 g/L, the volume was 250 mL and the optimum dosage of poly ferric silicate was 1.3 mL, the transmitting rate was 73.9% and the flocculation effect was b est.