The Si species distribution of inorganic polymer flocculant polyferric silicate sulfate (PFSS) was studied by chemical Si-Mo assay.The study included reaction rate characteristics and standard work curve of SiO2

polysilicic acid (PSi) species distribution characteristics at different pH values

and comparison of Si species distribution characteristics of PFSS and PSi at different pH values .The experimental results showed that Si species distribution characteristics in PFSS were variable at different pH values.The content of Sib of silicic acid in PFSS at pH values 1.46 and 1.70 was higher than that of silicic acid in PFSS at pH value 0.64

while the contents of high polymer state and gelatinous state in PFSS at pH value 0.64 were obviously higher than those in PFSS at pH values 1.46 and 1.70.Simultaneously

the study results also showed that PFSS at pH values 1.46 and 1.70 had better flocculability and stability than PFSS at pH value 0.64

therefore the superior state of silicic acid in PFSS was Sib.