Abstract: The objective of this study was to investigate the effects of alcohol precipitation and activated carbon adsorption on the structural and digestive characteristics of oyster hypoglycemic peptides (OHPs). The OHPs were subjected to alcohol precipitation and activated carbon adsorption treatments to increase their branched chain amino acid (BCAAs) content. The amino acid compositions and peptide sequences were analyzed using an amino acid composition analyzer and ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) technology. The in vitro hypoglycemic activity, including α-amylase, α-glucosidase, and dipeptidyl peptidase Ⅳ (DPP-Ⅳ) inhibitions, as well as peptide sequence characteristics of OHPs before and after gastrointestinal digestion was examined using an in vitro simulated digestion model to elucidate the digestive characteristics of OHPs. The results showed that the BCAAs content (increased from 55.30 mg/g to 122.87 mg/g) and proportion (increased from 15.78% to 18.77%) of OHPs after being treated by alcohol precipitation and activated carbon adsorption were significantly increased (P<0.05) compared to untreated OHPs. In addition, BCAAs were enriched at the N-terminal, while proline was localized near the C-terminal, showing a typical structural pattern of hypoglycemic peptides. After gastrointestinal digestion, OHPs exhibited a significant decrease in inhibitory activity against α-amylase and α-glucosidase (P<0.05), however, their inhibitory activity against DPP-Ⅳremained relatively stable. Moreover, the retention rates of OHPs' inhibitory activity against α-amylase and α-glucosidase were enhanced by alcohol precipitation and activated carbon adsorption treatments. The findings indicated that the alcohol precipitation and activated carbon adsorption effectively increased the BCAAs content of OHPs, resulting in a higher concentration of BCAAs at the N-terminus of their peptide chain. This improvement also facilitated the hypoglycemic activity retention of OHPs after digestion. In particular, the DPP-Ⅳ inhibitory peptide segments in OHPs exhibited good digestive stability.