The invention discloses a water absorbent resin suitable for a wood-pulp core and a preparing method thereof. The preparing method includes the following steps that after acrylic acid and deionized water are mixed, then a neutral reaction is carried out with a sodium hydroxide solution, the reaction is completed, then a sodium metasilicate water solution, acrylamide, a cross-linking agent and an initiating agent are sequentially added, and a milk-white mixed solution is obtained; nitrogen is introduced, mixed liquid is subjected to a polymerization reaction under ultraviolet rays, and transparent colloid is obtained; the colloid is granulated, dried and smashed, and resin powder is obtained; the resin powder is taken and evenly stirred with sodium metaaluminate, surface treatment liquid isadded for treatment, and the product is obtained. According to the water absorbent resin suitable for the wood-pulp core and the preparing method thereof, nanoscale silicon dioxide is generated in the neutral process and evenly dispersed in a reaction system and is capable of improving the liquid passing performance and the diffusivity of the water absorbent resin; the water absorbent resin prepared with the method is low in residual monomer, small in reverse osmosis amount, large in water retaining capacity, high in particle strength after water absorption, loose and particularly suitable for a wood-pulp-core paper diaper.