The invention discloses a method for improving the hydrophilicity of a polypeptide membrane by using polylactic acid and polyacrylic acid. The method comprises the following steps: (1) adding a polypeptide homopolymer, diisocyanate, a catalyst and a solvent into a dry reactor, reacting for 40-50 minutes at the temperature of 40-50 DEG C, and then, removing superfluous diisocyanate by a dialysis method, so as to obtain a polypeptide homopolymer containing terminal -NCO groups; (2) adding the polypeptide homopolymer containing terminal -NCO groups, a catalyst and a solvent into a dry reactor, then, adding polylactic-acid mono tetradecyl ether, and reacting for 50-60 minutes at the temperature of 40-50 DEG C, so as to obtain a polypeptide-polylactic acid diblock copolymer; (3) adding the polypeptide-polylactic acid diblock copolymer, polyacrylic acid and a solvent into a dry reactor, stirring and mixing for 60-70 minutes at the temperature of 40-50 DEG C, then, carrying out membrane forming by a tape casting method, and drying, thereby obtaining a target product of the method. According to the method, the preparation process is simple, and the hydrophilicity of the obtained modified membrane is improved greatly.