Objective To explore the possible mechanism of Yougui Yin in the treatment of steroid induced femoral head necrosis. Methods Thirty Sprague Dawley rats were randomly divided into normal control group

Yougui Yin group and hormone model group

with 10 rats in each group. Models of steroid induced necrosis of the femoral head were established by intraperitoneal injection of Escherichia coli endotoxin combined with intramuscular injection of methylprednisolone sodium succinate in hormone model group and Yougui Yin group. The normal control group received with the equal amount of saline injection. At the same time

Yougui Yin group was gavaged with 20 g /（ kg·d） of Yougui Yin for 8 consecutive weeks

while the hormone model group and the normal control group were gavaged with the equal volume of physiological saline. The general situation of rats in each group was observed

bone X-ray and bone mineral density were tested at the 4th and 8th weekend

and the serum levels of calcium and phosphorus were detected by the 8th weekend. Results Compared with the normal control group

the body weight of the rats in the hormone model group and Yougui Yin group was significantly decreased（ P < 0. 05） from the beginning of the 2nd week till the 8th week. Compared with hormone model group

the body weight of the rats in Yougui Yin group increased significantly（ P < 0. 05） from the 3rd to the 8th week. The mineral density levels of femoral shaft

femoral head and spine bone decreased significantly in the rats in the model group in the 4th and 8th week. However

the mineral density level of the femoral shaft

femoral head in the Yougui Yin group was significantly higher than that in the hormone model group in the 4th week（ P < 0. 01）

and the mineral density level of the femoral shaft

femoral head and spine bone in the Yougui Yin group in the 8th week was also significantly higher than that in the hormone model group（ P < 0. 01）. Compared with the normal control group

the level of serum calcium and phosphorus in Yougui Yin group and the hormone model group were decreased（ P < 0. 01）. Compared with the hormone model group

the level of serum calcium and phosphorus was elevated in Yougui Yin group（ P < 0. 01）. Conclusion Yougui Yin can significantly improve the bone mineral density in the femoral head necrosis model rats

and its mechanism may be related to the improvement of serum levels of calcium and phosphorus.