Composite filtrate reducer and preparation method thereof

The invention relates to the field of filtrate reducers, and particularly discloses a composite filtrate reducer and a preparation method thereof.The filtrate reducer is prepared from, by weight, 80-115 parts of composite resin, 30-50 parts of sodium carboxymethyl cellulose, 40-75 parts of gel particles and 2-6 parts of a coupling agent. The preparation method comprises the following steps: preparing composite resin: stirring and dissolving acrylamide, acrylic acid, hydroxyethyl acrylate, polyoxyethylene ether and sodium allylsulfonate, and adding a chain transfer agent and an initiator for reaction to obtain the composite resin; preparing gel particles: dissolving chitosan to obtain a chitosan solution, adding a silicon-containing inorganic substance, stirring and dispersing uniformly, and then adding aldehyde polysaccharide and a cross-linking agent for reaction to obtain the gel particles; and preparing the filtrate reducer: extruding and granulating the composite resin, sodium carboxymethyl cellulose, the