Abstract Laminarin is a tropical plant traditionally used in Chinese medicine. In this experiment, Laminarin polysaccharides were analysed using GC–MS method and result showed that the polysaccharides contained mannose (3.27%), arabinose (8.61%), glucose (4.23%), galactose (12.12%), fucose (46.93%). Laminarin polysaccharides were tested to evaluate their effect on lung oxidative stress and lipid peroxidation in rats. The animal were divided into model and polysaccharides-treated animal. Laminarin polysaccharides were administered by gavage over a 14-day period. The results indicated that Laminarin polysaccharides significantly normalized catalase (CAT) activity ( P < 0.01), increased glutathione peroxidase (GPx) activity ( P < 0.05), superoxide dismutase (SOD) activity and reduced malondialdehyde (MDA) concentrations in animal. It could be concluded that Laminarin polysaccharides appeared to be more effective in reducing sepsis-induced oxidative stress, lipid peroxidation in animal.