Abstract: To clarify the structural characteristics and antioxidant properties of the polysaccharides from Morinda citrifolia L. fruit, the crude polysaccharides from M. citrifolia fruit were extracted and purified by hot water leaching method. The structural characterization of purified polysaccharides was analyzed by infrared spectroscopy, nuclear magnetic resonance and gas chromatography mass spectrometry analysis. The ability of crude and purified polysaccharides to scavenge ABTS free radicals(·ABTS⁺), DPPH radicals(DPPH·), superoxide negative radicals(O₂^-·) and hydroxyl radicals(·OH) was measured by UV spectrophotometer, and the reducing power of polysaccharides was determined by the potassium ferricyanide reduction method. The results showed that the extraction rates of crude polysaccharide and purified polysaccharide were 9.48% and 0.35%, respectively, and the purified polysaccharide was mainly consisted of β-type glycosides, as well as a small amount of α-type glycosides, and contained uronic acids, which was an acidic sugar. Purified polysaccharides were polysaccharides with 1→4 linked pyranose glucose and non-reducing terminal pyranose as the main connection mode, and contained a branching structure. Both crude polysaccharide and purified polysaccharide could scavenge free radicals, where the scavenging ability of ·ABTS⁺ was the best, with the maximum scavenging rate reaching 100%, followed by DPPH· and ·OH, and the scavenging ability of O₂^-· was weaker. The scavenging ability of crude polysaccharides to free radicals was stronger than that of purified polysaccharides, and the scavenging capacity of crude polysaccharides for ·ABTS⁺ and DPPH· was comparable to that of the positive control Vc. Both crude polysaccharides and purified polysaccharides had reducing power, and showed a quantitative-effect relationship, and crude polysaccharides had stronger reducing power than that of purified polysaccharides.