The present invention provides one kind of water gel containing natural high molecular material and its preparation process. The water gel has cross-linking degree of 70-95 % and water absorption of 500-80000 %, and contains natural high molecular material or its derivative selected from chitin, chitin derivative, chitosan, chitosan derivative, carrageenin, etc. The water gel may have synthetic high molecular material, inorganic filler, cross-linking sensitizer, medicine and other assistant added. It is prepared through radiation cross-linking, with the radiation dosage being 10-40 kGy. The water gel of the present invention has high water absorption, high flexibility, good medicine slow releasing performance, and may be used in wound dressing, etc.