Soluble soybean polysaccharide-iron(Ⅲ) complex was synthesized by sodium citrate-FeCl3 method.The iron content was 18.1% using phenanthroline spectrophotometry.The results showed that soluble soybean polysaccharide and Fe3+ basically form a stable complex which doesn't precipitate at pH 1~14.The studies of antioxidant activity showed that,after reacting with iron,the hydroxyl radical-scavenging activity,nitrite scavenging activity and lipid peroxidation inhibition of soluble soybean polysaccharide were all getting better.At the concentration of 10mg/mL,hydroxyl radical-scavenging rate,sodium nitrite scavenging rate and lipid peroxidation inhibition rate of soluble soybean polysaccharide were 16.0%,53.9% and 34.9%,while soluble soybean polysaccharide-iron(Ⅲ) complex were 29.6%,67.5% and 77.9%.