Collagen is an important biomass resource, which has the characteristics of low antigenicity, hypoallergenicity, biodegradability, excellent biocompatibility and promoting cell proliferation and differentiation. Collagen peptides are generally composed of short sequences of 2 to 20 amino acid residues with a relative molecular mass of less than 10 ku. Through hydrolysis of macromolecule collagen, small molecule peptides are generated, which not only contain all amino acids of collagen, but also have better absorbability and processing characteristics than collagen, and are easier to be absorbed and utilized by the human body. In recent years, a variety of bioactive peptides have been isolated and identified from collagen peptides, such as antioxidant peptides, antihypertensive peptides, antibacterial peptides and so on. China is not only rich in aquatic resources, but also a big consumer of aquatic products. According to statistics, in 2022, the output of large-scale freshwater fish aquaculture in China is about 20.26 million tons, accounting for 62% of the total freshwater aquaculture in the country, of which the output of bighead fish aquaculture is firmly in the top three, reaching 3.27 million tons, and shows an overall growing trend, while the processing by-products of aquatic products are also increasing. In order to improve the high value utilization of Aristichthys nobilis bone, the best hydrolysis protease was selected with the A. nobilis head bone meal as raw material and the yield of collagen polypeptide as index, and the process of A. nobilis head bone collagen polypeptide was optimized. The amino acid composition, relative molecular weight, particle size, potential and microstructure of A. nobilis head bone collagen polypeptide were analyzed. The results showed that trypsin was the best hydrolysis enzyme for A. nobilis head bone meal, and the optimal hydrolysis process of bone collagen polypeptide was as follows: initial pH 8, enzyme dosage 2.5%, enzymolysis time 5 h, enzymolysis temperature 50 °C, solid-liquid ratio 1∶10 (g/mL). At this time, the yield of bone collagen polypeptide was 52.19%. The hydrolyzed polypeptide of A. nobilis head bone collagen contained 17 kinds of amino acids, among which the contents of glycine, proline, glutamic acid and alanine were (18.68±0.22), (10.06±0.09), (8.94±0.13) and (8.01±0.12) g/100 g, respectively. In line with the typical composition characteristics of collagen amino acids, the acidic amino acid content was 14.15 g/100 g, which had a high content and strong calcium binding ability. The relative molecular weight of A. nobilis head head collagen polypeptide was < 180 u, 500-180 u, 1 000-500 u, 2 000-1 000 u, 3 000-2 000 u and 5 000-3 000 u. The proportion of u was 2.26%, 21.04%, 44.40%, 22.02%, 4.86% and 3.23%, respectively, and the proportion of peptides below 5 000 u was as high as 97.81%, indicating that the products of enzymatic hydrolysis were mainly small molecular peptides with high absorption rate and high affinity for stomach and intestines. The average Z-particle size of A. nobilis head bone collagen polypeptide was (399.90±2.70) nm, and the polydispersion index (PDI) was 0.40±0.01, which was between monodisperse system and medium disperse system (0.30-0.50), indicating that the substance distribution was uniform, and the intercept was close to 1, indicating that the particle size distribution curve was well fitted. The surface of A. nobilis head bone collagen polypeptide particles was negatively charged. The A. nobilis head bone collagen polypeptide is loose in structure, porous and uneven in size, and has a lamellar structure. Studies have shown that A. nobilis head bone collagen polypeptide is rich in nutrients, its small molecule peptide is easy to be absorbed by the human body, and its loose porous structure is also conducive to the preparation of peptide calcium chelates. This study not only provides theoretical basis for the intensive processing of A. nobilis bone products, but also provides excellent raw materials for the preparation of new calcium preparations.