The invention discloses hydrogel dressing which is composed of an upper layer and a lower layer. The lower-layer hydrogel is prepared by utilizing freeze thawing radiation method, and the upper-layer hydrogel is prepared by utilizing the radiation method; both the layers of hydrogel contain water-soluble polymer, and solvent for the residual; wherein, the lower-layer hydrogel contains polyvinyl alcohol. The invention also discloses a hydrogel-dressing preparation method which comprises the following steps: after the deaeration treatment of the water-soluble polymer solution containing polyvinyl alcohol, the hydrogel is prepared by utilizing circulating frozen thawing method; the water-soluble polymer solution after the deaeration treatment is positioned on the hydrogel, and then irradiation is performed under the high-energy rays. The hydrogel dressing has not only excellent strength and toughness, but also high transparence and wound fluid absorption ability. Meanwhile, the hydrogel dressing requires no additional chemical cross-linking agent or initiating agent, medical adhesive, and no reinforcing layer, such as fiber fabrics and woven fabrics, the two layers can be bonded firmly, and the preparation and the disinfection can be finished synchronously.