To enhance the utilization value of Seriola lalandi bone resources, this study investigated the effects of demineralization treatment on collagen-peptide preparation from S. lalandi bones. Collagen peptides were prepared from demineralized S. lalandi bone (DMB) and mineralized S. lalandi (MB) via alkaline protease hydrolysis. Through analyses of molecular-weight distribution, amino acid composition, infrared spectroscopy, and functional properties, the study revealed that demineralization treatment (0.50 mol•L-1 hydrochloric acid) increased the proportion of <1 000 Da oligopeptides to 75.96%, while decreasing the weight-average molecular weight from 587 to 441 Da. DMB collagen peptides showed significant enrichment of glycine (313 residues per 1 000) and amino acids (174 residues per 1 000), with a 3.8 cm-1 blue shift in the amide A band, indicating improved molecular regularity. In terms of functional properties, DMB collagen peptides exhibited a water absorption capacity of 96.14% and a water-holding capacity of 65.33%, representing increases of 16.09% and 10.09% compared to MB collagen peptides, respectively. Its oil absorption capacity decreased from 4.63 to 4.32 mL•g-1, while the content of the characteristic tripeptide X-Hyp-Gly increased by 11.23%, suggesting enhanced bioactivity. These results demonstrate that demineralization treatment significantly improves the proportion of small-molecule peptides, amino acid compositional regularity, water absorption capacity, and waterholding capacity of S. lalandi bone collagen peptides. This study contributes to enhancing the utilization value of S. lalandi bone resources, offering a theoretical foundation and technical support for their application in the food industry.