In north for low molecular weight heparin sodium heparin preparations, can make the anti-clotting factors Ⅹ a and Ⅱ ratio greater than 4 a vitality, so as to play a strong function of anti thrombosis and dissolve thrombus. There was no significant change in total coagulation index, platelet aggregation time and fibrinogen binding at the recommended dose. Although low molecular weight heparin (LMWH) is applicable to all heparin fragments with a molecular weight of less than 8000 Da, the effect of each fragment is still determined by the molecular weight. In vitro studies comparing enoxaparin sodium (molecular weight 4000 ~ 6000 Da) with unseparated heparin showed that the inhibitory effect of enoxaparin sodium on thrombin decreased by about 5 times according to their respective molecular weight compared with that of unseparated heparin. In vivo studies have also shown that when heparin is applied subcutaneously, the partial thromboplastin activation time (APTT) is significantly longer than when enoxaparin sodium is applied subcutaneously.