The invention relates to a compound salt-tolerant absorbent resin and a preparation method thereof. The compound salt-tolerant absorbent resin is prepared through copolymerizing the following five raw materials: a first raw material which is acrylamide or (sodium) acrylate; a second raw material which is a cationic monomer; a third raw material which is one of vinyl acetate and hydroxyethyl methylacrylate; a fourth raw material which is a multi-unsaturated bond function monomer; and a fifth raw material which is an inorganic filler. The absorbent resin is basically neutral, has low price, high strength and excellent salt tolerance, and can be directly applied to agriculture and forestry users. A redox system is adopted to initiate the polymerization, and can guarantee the implementation of the reaction at a low temperature.