The invention discloses a making method of high-hydroscopicity resin, which comprises the following steps: adding neutralizing agent and internal crosslinking agent in the insaturated monomer liquid; adding high-high-hydroscopicity resin to catch polyvalent metal ion; adding starter in the insaturated monomer solution; proceeding free-radical polymerization; cutting the gel; drying; grinding; sieving the fixed grain size; adding surface crosslinking agent; heating.