The invention discloses a low-cost flocculating agent. The low-cost flocculating agent comprises, by mass, 30-43 parts of a silicate solution, 10-35 parts of triethylamine, 8-10 parts of starch, 6-15 parts of carboxymethylcellulose sodium, 8-16 parts of anhydrous ethanol, 30-43 parts of ammonium persulfate, 30-43 parts of sodium carbonate, 30-43 parts of iron citrate, 3-10 parts of ethylenediamine, 15-25 parts of sulfuric acid, 20-35 parts of a sodium hydroxide solution, 30-45 parts of an iron salt agent solution, 3-5 parts of polyacrylamide, 15-25 parts of magnesium chloride, 9-18 parts of sodium oxide, 8-12 parts of acrylic acid, 9-15 parts of monohexadecyl maleate sodium salt and 30-50 parts of deionized water. The prepared water treatment flocculating agent has the advantages of increased viscosity, good stability, convenience for industrial production, safety, environmental protection, low cost, simple technology, high-efficiency flocculation effect, and realization of effective removal of colloids and suspension particles in water.