Abstract: It is the first time to investigate effects, on the blood rheology and the protection on oxidative damage in myocardium in tail-suspended rats of Drageny I, which is a kind of rare TCM herbs. SD rats are randomly divided into three groups: control group, model group and drug group.The blood rheology and the oxidative damage(the level of H<sub<2</sub<O<sub<2</sub<,MDA and T-SOD) of myocardium are examined in ways as follows:veinal blood and myocardium test after 5 d and 21 d tail-suspension respectively. Compared with the model group, the hematocrit and the level of myocardium MDA in drug group decrease significantly after 5 d of tail-suspension. Red blood cell maximum deformation index, whole blood viscosity, the level of H<sub<2</sub<O<sub<2</sub< and T-SOD of myocardium show no significant changes. After 21 d of tail-suspension, whole blood viscosity of the drug group decreases significantly while red blood cell maximum deformation index increases remarkably. Other indexes show recovery tendency. Drageny I significantly inhibits the increase in hematocrit and blood viscosity while increasing the red blood cell maximum deformation index in tail-suspended rats. It also shows protective effects on the myocardium from oxidative stress in rats under the simulated microgravity condition.