Abstract: A new composite polymer,Si-Fe coagulant with various Si/Fe molar ratios,was prepared by using water glass,ferrous sulfate and sodium chlorate by copolymerization.Charged properties of PSF samples taken from different copolymerization times and influence of dilution concentration on PSF Zeta potential were studied with Nano Zetasizer.The pollutants removal by PSF in treating lower temperature and lower turbidity water,and slaughterhouse effluent was explored compared to that by polyferric aluminum (PFA).Results show that the copolymerization between Si and Fe is not a simple electro neutrality process between positive charge of Fe and negative charge of polysilicic acid (PS).PSF is found to be a complexation compound of Si,Fe and many other ions,instead of a simple mixture of raw materials.The Zeta potential of PSF at higher concentration tends to be zero,and tends to increase when diluted,up to 11 mV,whereas the average Zeta potential of PFA is 36.1 mV,and slightly increases when diluted.For lower temperature and lower turbidity water,PSF gives higher COD_Mn removal by 20% than PFA,and for slaughterhouse effluent,PSF has higher turbidity,COD_Cr and color removal by 60%、66% and 54% than PFA,respectively.The coagulation mechanism of PSF is the cooperation of charge-neutralization /destabilization,bridging and sweeping.