Fish skin is the main by-product of aquaculture processing， which has attracted much attention due to its low utilization rate. To better understand the antioxidant activity and structural properties of different fish skin peptides， salmon skin， sturgeon skin and bighead carp skin were hydrolyzed by alcalase. The degree of hydrolysis (DH)， trichloroacetic acid-nitrogen solution index (TCA-NSI) and molecular weight of fish skin peptides were evaluated， and the antioxidant activities of fish skin peptides were examined based on 1， 1-diphenyl-2-trinitrophenylhydrazine (DPPH) radical scavenging rate， ·OH radical scavenging rate， Fe2+ chelating activity and reducing power， and the structural properties of the three fish skin peptides were compared. The results showed that sturgeon skin peptides had the highest DH (22.34%) and TCA-NSI (48.65%) and the lowest molecular weight， indicating the best hydrolysis. The antioxidant activity of the three fish skin peptides was concentration-dependent， with sturgeon skin peptides having significantly higher antioxidant activity than sturgeon skin peptides and bighead carp peptides (P < 0.05). The sturgeon skin peptides had higher hydrophobicity and fluorescence intensity and contained higher content of hydrophobic amino acids， which had positive effects on the antioxidant activity. Fourier transform infrared spectroscopy confirmed some differences in the internal microenvironment and protein secondary structure of different fish skin peptides， resulting in a greater variation in antioxidant activity. This study can provide some theoretical basis for the preparation and development of fish skin peptides for application.