Method for preparing hydrolyzed polyacrylonitrile filtrate reducer by cross-linking inorganic metal ions

The invention relates to a method for preparing a hydrolyzed polyacrylonitrile filtrate reducer by cross-linking inorganic metal ions, which comprises the following steps of taking NaOH as a catalyst, taking trivalent aluminum salts or trivalent iron salts as a crosslinking agent, and hydrolytically reacting with a waste acrylic raw material to obtain jelly; and drying the jelly at a temperature of 100 to 110 DEG C, crushing and screening to obtain the filtrate reducer, wherein the NaOH is 10 to 30%, the trivalent aluminum salts or trivalent iron salts are 1 to 7%, the waste acrylic is 25 to 40%, and the balance is water. The filtrate reducer has good water-solubility, low filtration, stable quality, simple processing technology, and environment friendliness, and is easy for industrial scale production.