A new type of inorganic polymer flocculant polysilicate ferric(PSF) was prepared by using pyrite slag as raw materials and used as flocculant in the treatment of tanning wastewater. The infrared spectrometry and X-ray diffraction had been adopted to characterize the product structure. The infrared spectrometry research indicates that Fe-O, Si-O-Fe and other groups exist in the PSF, which implies that chemical bonding reaction takes place between Fe and silicon in the PSF. X-ray diffraction analysis indicates that PSF is the amorphous polymer created upon mutual reaction between Fe3+ and PSi. The application experiment results show that the removal rate of S2-, SS, CODCr, Cr3+, and colority is 92.7%, 90.5%, 82.5％, 80.2% and 90.1% respectively in the condition where temperature is normal, pH value is 7.5 and dosage of the coagulant is 80mg/L. The flocculation effects of PSF in the treatment of tanning wastewater are much better than those of PAC and PFS.