A series of composite packaging films of soy protein isolate and polyvinyl alcohol plasticized by glycerol were prepared in acidic medium by using the solvent evaporation method with fumaric acid as a cross-linking agent. The composite films obtained were tested in terms of FTIR, tensile property, light transmittance, moisture content, and water resistance. Results showed that the composite films exhibit high tensile strength after cross-linked along with promoted elongation if added with glycerol; the films has much good transparency with light transmission rate of up to 88. 6% ; the addition of fumaric acid has less effect on the film moisture retention and water resistance while the introduction of glycerol can significantly increase the film water content and total soluble matter contents.