NOVELTY - Extraction of antibacterial peptide comprises collecting 2-3 L fresh pig blood and using 5% sodium citrate as anticoagulant, grinding fresh pig blood at 37 degrees C, standing in incubator for 2 hours, adding 0.84% ammonium chloride solution, ultrasonically treating for 50 times, centrifuging, re-suspending deposition in 10% acetic acid, fully mixing uniformly, extracting solution, purifying, concentrating peptide, intercepting molecule, mixing eluent with 0.5% methanol, and filtering to obtain solution.    USE - Method of extraction of antibacterial peptide (claimed) used in antimicrobial medicine.    ADVANTAGE - The method produces peptide having strong antibacterial activity, natural, non-toxic, non-pollution, no residue and no side effect, green, broad-spectrum antibacterial, antivirus, does not produce drug resistance, and immune regulating effect function.    DETAILED DESCRIPTION - Extraction of antibacterial peptide comprises:    (A) collecting 2-3 L fresh pig blood and using 5% sodium citrate as anticoagulant;    (B) grinding fresh pig blood at 37 degrees C, standing in incubator for 2 hours, adding 0.84% ammonium chloride solution, mixing uniformly, standing for 3 minutes, centrifuging at 400 revolutions/minute for 10 minutes, adding supernatant and ammonium chloride solution, mixing uniformly, standing for 3 minutes, centrifuging for 500 revolutions/minute for 10 minutes, removing supernatant, mixing precipitate with cold physiological saline at 4 degrees C, adding 200 ml 10% glacial acetic acid, precipitating, fully mixing uniformly, pouring into 50 ml beaker, ultrasonically treating for 50 times, magnetically stirring solution, centrifuging at 15000 revolutions/minute for 30 minutes, re-suspending deposition in 10% acetic acid, fully mixing uniformly, extracting solution, and centrifuging for 15000 revolutions/minute for 30 minutes;    (C) adding solution into dialysis bag, binding bag opening, putting into beaker, pouring in distilled water to beaker in distilled water, adding acid, changing water until penetrating in bag at pH 6, putting dialysis bag in porcelain, spreading polyethylene glycol 6000, dialyzing for 3-4 hours, freeze-drying at low temperature, taking out penicillin bottle, sealing and storing at 20 degrees C;    (D) separating peptide, dissolving frozen sample with 0.5% methanol, processing chromatography with chromatographic column sephadex gel, collecting eluent, collecting solution with ultraviolet light, measuring absorbance of absorption value 280 nm, cyan packing in penicillin bottle, drying at low temperature in freeze dryer at 280 nm with absorption of solution, storing at 80 degrees C, taking 20 mg sample, dissolving in sterilized distilled water sample with micropore filter film filter sample, soaking with drug sensitive paper overnight, screening, collecting, and culturing at 5 degrees C; and    (E) purifying, concentrating peptide using ultra-filtration device, intercepting molecule amount of 20 kD, mixing eluent with 0.5% methanol, and filtering to obtain solution.