To evaluate the effect of degradation on the structure and properties of sea buckthorn polysaccharides (SBP), the H₂O₂ combined with Fe²⁺ method was used to degrade SBP. The effects of degradation on the molecular weight, monosaccharide composition, particle size, structural characteristics and antioxidant capacity of sea buckthorn degraded polysaccharides (SBDP) were investigated. The results showed that, the molecular weight of SBDP (2.902×10⁴Da) was significantly lower than that of SBP (3.016×10⁵Da). Ion chromatography analysis proved that both SBDP and SBP were composed of the same monosaccharides (fucose, rhamnose, arabinose, galactose, glucose, mannose and galacturonic acid) in different molar ratios. SBDP showed similar structural characteristics to SBP as confirmed by FTIR and NMR spectroscopy. The solubility of SBDP was increased by 20.72%, and SBDP had better hygroscopicity and moisture retention. SBDP had lower apparent viscosity (5.0mg·mL-1) and shear thinning behavior. SBDP exhibited higher antioxidant activity, with the DPPH radical, ABTS⁺ radical and hydroxyl radical scavenging rates of 89.44%±0.12%, 96.09%±0.22% and 73.26%±1.16%, respectively. The H₂O₂ combined with Fe²⁺ treatment significantly reduced the molecular weight of SBP and enhanced its functional properties and antioxidant activity. This research aimed to expand the application of SBP in food applications.