How to increase the ability of charge neutrality of flocculant is one of the exploring hot points in water treatment. Adding Sn4+ in coplymeriting of Fe3+ to increse the charge of the copolymer was studied in this paper. The chemical characteristics and crystal image of the copolymer were also studied by potentiometric titration in copolymeriting and scanning electron micrograph. Essential experimental basis for further researching copolymerization of Fe( Ⅲ ) and Sn( Ⅳ) was put forward.