Using potato starch as raw material, the starch was modified by biological method. Pullulanase can spe-cifically cut the α-1,6 glycosidic bond of the starch branch to increase the amylose content, thereby im-proving the performance of the starch film. Using Urea as plasticizer, starch nanocrystal (SNC) and nano zinc oxide (ZnO) as composite reinforcing agents, the composite film is prepared by casting method. The effects of the type and amount of plasticizer and the type and amount of reinforcing agent on the proper-ties of the composite membrane were investigated by single factor experiments. The amylolytic process was explored by orthogonal experiment. The optimal enzymatic hydrolysis process of potato starch was obtained by using the tensile strength of the composite membrane as the index: enzyme dosage 0.8U/g, reaction temperature 50 °C, pH 4.0, reaction time 2h. Compared with the non-enzymatic composite membrane, the tensile strength of potato starch composite film increased by 19%, the elongation at break increased by 42.8%, the transparency increased by 5.6%, the haze decreased by 67.4%, and the water vapor transmission coefficient decreased by 98.4%, Oil permeability coefficient decreased by 52.6%.