Flocculant for preparing purified water and preparation method of flocculant

The invention provides a flocculant for preparing purified water. The flocculant is prepared from, by weight, 40-60 parts of ferrous sulfate, 0.6-1 part of ammonium ferric sulfate, 0.2-0.4 part of trimethylsilyl methanesulfonate, 3-5 parts of 2-amino-1,3-propanediol and the like. The flocculant is good in flocculation effect and convenient to use.