The acetylation modification of blackcurrant fruit polysaccharide (BP) was carried out by using acetic anhydride. The acetylated polysaccharides with low, medium and high degrees of substitution including ABP-1 (DS = 0.14±0.02) , ABP-2 (DS = 0.28±0.02) and ABP-3 (DS = 0.55±0.01) , were selected to study the effects of acetylation modification on the structural characteristics (monosaccharide composition and morphological features) and bioactivities of BP. FT-IR analysis and GC analysis confirmed that the acetylation modification had no effect on the main structure of BP, and ABP-1, ABP-2, ABP-3 contained the same monosaccharide species (galacturonic acid, rhamnose, arabinose, xylose, mannose, glucose, galactose) as those of BP but at different molar ratios. The Congo red test showed that the acetylated polysaccharides and BP had no triple helix structure, SEM analysis indicated that the surface morphology of acetylated polysaccharides was different from that of BP. The activity test results showed that the acetylated polysaccharides had strong free radical (DPPH·, OH·, O2-·) scavenging ,α-amylase and α-glucosidase inhibitory activities. The order was: BP < ABP-1 < ABP-2 < ABP-3 < positive control（Vc or acarbose）. The results of α-glucosidase inhibition kinetics showed that the inhibitory effects of BP and acetylated polysaccharides on α-amylase were reversible and exhibited a competitively inhibitory process.