The invention discloses a preparation method of a high-diffusivity water-absorbent resin. The preparation method comprises the following steps: adding acrylic acid, a 50% sodium hydroxide solution, a compound cross-linker, sodium bicarbonate, ethanol, silicon dioxide and deionized water to a reactor, mixing evenly, and then introducing nitrogen for 20 min to remove oxygen; next, adding an initiator at a temperature within the range of 5-10 DEG C to initiate a polymerization reaction, terminating the reaction when the temperature stops rising, and preserving heat for 2 hours at a temperature above 80 DEG C, thereby obtaining polymeric colloid; pelleting the colloid to obtain resin particles and drying at 180 DEG C until the moisture content is lower than 3%; and finally, evenly spraying a surface treating fluid to the particles for surface treatment, and preserving heat at 180 DEG C for 40 minutes, thereby obtaining the product. According to the preparation method of the high-diffusivity water-absorbent resin, the resin particles are of a loose porous structure, numerous pore passages are formed inside the resin particles and the contact area is greatly increased, and therefore, the high-diffusivity water-absorbent resin has an instantaneous absorption effect; and the pore passages are in contact and connected in series with each other, and due to the capillary action, moisture can be transferred among the particles smoothly.