Preparation method of water absorption resin

The invention discloses a preparation method of water absorption resin. The preparation method mainly comprises the following steps: (a) adding acrylic acid with a neutralization degree of 60 to 80 percent and a mass concentration of 30 to 45 percent and/or an acrylate aqueous solution as well as water absorption resin powder, inorganic particles and a surface active agent into a reactor, and uniformly stirring; (b) adding a cross-linking agent and an initiator, and facilitating reaction to form gel; (c) crushing the gel, then drying the gel by utilizing hot air of 100 to 200 DEG C, grinding the gel, screening and grading the ground gel to obtain particles of 150 to 850 micrometers; (d) adding water and a surface cross-linking agent under 100 to 230 DEG C, and carrying out the surface treatment for 10 to 100 minutes to obtain the water absorption resin. In the preparation method, a polyacrylic acid formed by polymerizing the water absorption resin powder and a neutralization solution and/or a polyacylate network to form a double-network structure, so that the mechanical performance and quality of a product can be greatly improved; small-particle-size water absorption resin which is removed in a grading step is re-added into a polymerization step, so that the productivity of the water absorption resin and a product yield are improved, and the production cost is reduced.