The invention discloses a method for preparing an anion template flocculant TPAS (Tissue Plasmogen Activator). The method comprises the following steps: with ultrasonic waves as an initialization mode, and by taking acrylamide and sodium p-styrenesulfonate as main raw materials, and polypropylene ammonium chloride PAAC (Polyallyl Acetate) as a template agent, preparing a water solution, adjustingthe pH value by using sodium hydroxide or hydrochloric acid, introducing a sufficient amount of nitrogen, initializing a polymerization reaction in an ultrasonic reactor, after the reaction is completed, performing aging treatment in a water bath pot, taking out a polymer obtained through synthesis, cleaning with alcohol, drying, and powdering, thereby obtaining the anion template flocculant TPAS.The method is simple in process procedure, short in reaction cycle, free of damage to instrument equipment, safe and environmental-friendly, free of toxic or side effect, low in cost, excellent in product property, and good in flocculation effect in treating hematite wastewater.