A new polyferric silicate chloride(PFSC) was prepared by using sodium silicate, ferric chloride as raw materials, at the same time, its coagulation performance and the influencing factors were observed. The water containing algae was processed by PFSC coagulant and coagulation mechanism were discussed. The results showed that the best reaction time of PFSC preparation was 1h, temperature was 40°Cand Fe/Si mole ratio was 1. The removal efficiencies of chlorophyll a and turbidity were 82.40% and 94.97% respectively at 14mgFe•L-1 of dosage. Coagulation mechanism of PFSC is considered as the cooperation of oxidization/adsorption/charge-neutralization, adsorption-bridging and sweeping, which is the effect of silicic acid, iron and iron hydrolysate on the suspended particles in wastewater.