Using potato starch as the basic skeleton, small molecule acrylic acid (AA), structurally elastic straight pullulan (PULL) as raw material in the environment of potassium persulfate as initiator, N,N'-methylenebisacrylamide as cross-linking agent, the starch-acrylate-pullulan semi-interpenetrating network polymer (st-AA-PULL) was prepared by two-step aqueous solution microwave method.FTIR, SEM, and BET were used to analyze the molecular structure characteristics, and the hydration characteristics of the product were investigated. The results of hydration characteristics showed that the swelling rate of distilled water by st-AA-PULL was as high as 1333 g/g, and the swelling rate of tap water and physiological saline were 536 g/g and 126 g/g, respectively;the semi-interpenetrating network material has better water retention compared with traditional polymeric materials ,it retains nearly 30% of moisture after standing at 60℃ for 90 min. The water absorption rate can still reach nearly 60% after repeating the water absorption five times; and the NaCl salt tolerance is also greatly improved in the concentration range of 0.02 to 0.10 mol/L，the equilibrium swelling ratio was maintained at 130 g/g at salt concentration of 0.10 mol/L.