BACKGROUND Laminaria japonica polysaccharide (LJP), a fucose enriched sulfated polysaccharide has been demonstrated to have excellent anticoagulant and antithrombotic activities. However, the antithrombotic effect of low molecular weight polysaccharide from enzymatically modified of LJP (LMWEP) remains unknown. MATERIAL AND METHODS LMWEP was prepared by fucoidanase enzymatic hydrolysis, and the antithrombotic and anticoagulant activities, and the underlying mechanism were investigated thoroughly. Rats were randomly divided into 6 groups (8 rats in each group): the blank control group, the blank control group treated with LMWEP (20 mg/kg), the model group, the model group treated with heparin (2 mg/kg), the model group treated with LJP (20 mg/kg), and the model group treated with LMWEP (20 mg/kg). After 7 days of intravenous administration, blood was collected for biochemical parameters examinations. RESULTS LMWEP increased the activated partial thromboplastin time (APTT), thrombin time (TT), prothrombin time (PT), 6-keto prostaglandin F1alpha (6-Keto-PGF1alpha), and endothelial nitric oxide synthase (eNOS). In addition, LMWEP decreased fibrinogen (FIB), endothelin-1 (ET-1), thromboxane B2 (TXB2), erythrocyte sedimentation rate (ESR), and hematocrit (HCT). CONCLUSIONS LMWEP, an enzymatically modified fragment with a molecular weight of 25.8 kDa, is a potential antithrombotic candidate for treatment of thrombosis related diseases.