The invention discloses a method for preparing protein stuffing for tanning with chrome-containing scrap leather from tanning, which is characterized in that the method comprises the following steps: rubbing the chrome-containing scrap leather from tanning and taking 100 parts, then immersing the chrome-containing scrap leather into 0.3-1.5 wt% of alkaline compound solution that at least can submerse the scrap leather for 15-45 hours, and draining; putting the pre-treated chrome-containing scrap leather into a reaction kettle equipped with a stirrer, a thermometer, and a reflux condenser; adding 8-18 parts of alkaline compound and water that at least can submerse the chrome-containing scrap leather, raising the temperature to 55-90 DEG C, and keeping for 3-18 hours to obtain thick liquid with deep color; cooling the liquid and adjusting the pH value with inorganic acid to 6-7, then filtering to obtain collagen polypeptide-rich filtrate with a solid content of 10-20%; adding 0.2-0.5 wt% of polycarboxylic acid-N-hydroxysuccinimide based on the weight of the dry basis of collagen polypeptide, and reacting at room temperature under continuously stirring for 1-3 hours; and concentrating and drying to obtain the protein stuffing for tanning.