Abstract: The biodegradable composite films were prepared by cross-linked reaction with chitosan,polyvinyl alcohol(PVA) and starch as raw materials in this paper.The effects of cross-linking reagents such as formaldehyde,glutaraldehyde and glyoxal on the properties of the films during preparation were investigated in detail.Results showed that pH had great effect on the properties of cross-linked films.The reaction was quick and its compatibility increased under strong acidic condition.The tensile strength and the percentage of breaking elongation of the films decreased with the the pH,increase of pH high level also led to the increase of water-retaining rate and water-permeability rate of the films cross-linked by formaldehyde and glyoxal and the decrease of water-retaining rate and water-permeability rate of the films cross-linked by glutaraldehyde.The color of the films cross-linked by glutaraldehyde and glyoxal varied with the variation of pH.The properties of the films were also affected by the dosage of aldehydes.If the dosage in-(creased,) the tensile strength and the percentage of breaking elongation of the films increased firstly and then decreased,but the water-retainig rate and water-permeability rate decreased gradually.Superfluous aldehydes could impair the properties,whereas the existance of aldehydes is favorable to compatibility of the films.