In this paper,research on the preparation of Mg-Fe composite flocculant（PFMS） was conducted.And the Mg-Fe composite flocculants product with good quality was obtained. The structure and iron distribution of the product were investigated,respectively.Finally,the flocculation performance difference between self-made PFMS\PFS and industrial PFS is investigated.1.A new PFMS composite flocculant was prepared by ferrous sulfate（FeSO₄）, magnesium oxide（MgO） and sulfuric acid（H₂SO₄）.Effect of temperature,dosage of oxidant, sulfuric acid and the molar ratio of MgO on flocculating properties was investigated, respectively.The optimum condition of preparation of PFMS was shown,the reaction temperature is 30℃,the molar ratios are n（ClO₃^-）:n（Fe）=1:6,n（H₂SO₄）:n（Fe）=0.3;MgO= 30%.2.The structure and iron distribution of the product were investigated.A ferron-complexation timed spectrophotometric method was used to determine the distribution of different Fe（Ⅲ）.The structural differences between PFMS and PFS were observed by characterization means of Fourier Transform Infrared Spectroscopy.The Magnesium ion didn’t participate in the polymerization process,but it improved the stability of the product.3.In order to study the flocculation performance difference between self-made PFMS\PFS and industrial PFS,the simulated turbidity wastewater by kaolin,the simulated dye wastewater by Direct Fast Black G and the coking wastewater were chosen to carry out the coagulation experiment of removing turbidity,color and COD,respectively.The turbidity removal efficiency by PFMS was a little higher than that of the self-made and industrial PFS, the residual turbidity was blow 5 NTU.In alkaline conditions,the decoloration rate and COD removal rate by PFMS were higher than that of the self-made and industrial PFS.