The invention relates to a method for preparing silk fibroin film, especially a method for using covalence decoration to prepare novel antibiosis silk fibroin film. The inventive method comprises that removing foreign materials of Na2CO3 solution smelted silk fibroin, dissolving in lithium bromide water solution, drying, mixing alcohol with water, immerging in phosphate buffer solution, immerging in EDC HCl/NHS solution, immerging and washing in phosphate buffer solution, drying. The invention can adjust the density of silk fibroin, the density of antibiosis peptide solution and process covalence decoration, to control the antibiosis function. The invention has the structure and functions of natural animal silk fibroin, with surface antibiosis activity, long service life and non drug tolerance.