The invention discloses a preparation method of a medical hydrogel wound dressing, 20 to 30 percent by weight of sodium polyacrylate, 2 to 6 percent by weight of polyvinyl alcohol and 60 to 78 percent by weight of water are taken as raw materials, the medical hydrogel wound dressing is obtained by casting, radiation cross-linking grafting and sterilization, the radiation dose rate is 15kGy / time, and the dose is 30 to 90kGy. The hydrogel wound dressing obtained by the invention has very high swelling degree and can greatly reduce the replacement of the dressing and be doped with a cell growth factor for slow release, thus being the ideal wound dressing for treating various burns, scalds, trauma wounds and other wounds, more particularly, the large-area and hypertonic skin wounds; furthermore, the preparation process is simple and the cost is slow, thus having good industrial application prospect.