In this study， Lepidotrigla microptera was used as the experimental material to prepare protein peptides， and the effects of in vitro digestion on the activity and structural characteristics of ACE-inhibitory peptides were investigated. Ultraviolet-visible(UV) absorption spectroscopy， fluorescence spectroscopy， Fourier transform infrared spectroscopy (FTIR)， and high-performance liquid chromatography (HPLC) were employed to analyze changes in the activity and structure of Lepidotrigla microptera protein peptides during gastrointestinal digestion. The results showed that after in vitro digestion， the IC50 value of the ACE inhibition activity of Lepidotrigla microptera protein peptides decreased to (0.62±0.015) mg/mL， the proportion of components with a molecular mass less than 1 000 u increased to 89.96%， and the free amino acid content increased to 634.41 mg/g. Additionally， digestion led to the cleavage of peptide bonds， loosening of the molecular structure， and exposure of aromatic amino acid residues， resulting in a change in protein conformation， increased surface hydrophobicity， and an increase in α-helix and β-sheet content to (19.55±0.28)% and (15.29±0.22)%， respectively. In conclusion， gastrointestinal digestion altered the structure of Lepidotrigla microptera protein peptides， resulting in enhanced antihypertensive activity. These findings suggest that Lepidotrigla microptera protein peptides exhibit good digestive stability. This study provides a theoretical foundation for the application of ACE-inhibitory peptides from Lepidotrigla microptera in the food industry.