NOVELTY - Method for preparing odorless moisture-retaining collagen involves taking fish skin, adding water and % calcium hydroxide, stirring and soaking for 5-6 days, washing with water, and soaking in sodium chloride solution at 4-6 degrees C for 6-8 hours, adding water, Bacillus subtilis alkaline protease, Flavourzyme (RTM: fungal protease/ peptidase complex), and M0111-9 enzymolysis protecting agent, enzymolyzing, inactivating, centrifuging, removing solid residues, adding activated carbon to the filtrate for bleaching, and concentrating by spray-drying.    USE - The method is useful for preparing odorless moisture-retaining collagen useful as additive in skin-care products.    ADVANTAGE - The method is simple, easy, environmentally-friendly and safe, provides odorless moisture-retaining collagen having excellent bioactivity and quality, does not generate wastewater, uses mild reaction conditions, and is suitable for industrial production. The product is non-irritating, increases skin elasticity, retains skin moisture, and improves skin conditions.    DETAILED DESCRIPTION - Method for preparing odorless moisture-retaining collagen involves taking fish skin, adding 5-7 times water and 4-4.5% calcium hydroxide, stirring and soaking for 5-6 days, washing with water, and soaking in 2.2-2.4% sodium chloride solution at 4-6 degrees C for 6-8 hours, adding 5-7 times water, 0.6-0.8 %mass Bacillus subtilis alkaline protease, 0.6-0.8 %mass Flavourzyme (RTM: fungal protease/ peptidase complex), and 0.2-0.3 wt.% M0111-9 enzymolysis protecting agent, enzymolyzing at pH 6-7 and 50-55 degrees C for 2.5-3 hours, inactivating by heating at 85-89 degrees C, centrifuging at 4200-4400 rpm for 12-14 minutes, removing solid residues, adding 0.5-0.5% w/v activated carbon to the filtrate for bleaching at 55-60 degrees C for 50-55 minutes at pH 5-6, and concentrating collagen solution by spray-drying to obtain purified product of collagen peptide with a relative molecular mass of 5000 Da.