Abstract: Objective To observe the changes of contents of indexes of coagulation-fibrinolysis systems of steroid-induced avascular necrosis of femoral head ( SANFH) in rabbits before and after hyperbaric oxygen (HBO) treatment and to investigate the mechanism of action of early HBO treatment on SANFH . Methods Animal models of steroid-induced avascular necrosis of femoral head were established, then contents of antithrombin-Ⅲ(AT-Ⅲ), thrombomodulin(TM) , tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor-1 ( PAI-1) were measured in each group respectively. Results The content of AT-Ⅲ in HBO group was significantly higher than that in model group at four and six weeks( P <0.01). The content of TM in HBO group was significantly lower than that in model group at one week(P <0. 05), whereas higher at four weeks (P < 0.05). At two weeks, the content of tPA in HBO group was significantly higher than that in model group(P<0. 05) , whereas that of PAI-1 lower (P < 0. 05). Conclusions Early HBO therapy can relieve endothelial cell injury of blood vessel, promote synthesize and discharge of anticoagulative factor and accelerate dissolution of fibrin, which improve hypercoagulability state of model animals of SANFH.