[Objective] To investigate the efficacy and potential mechanism of human ?umbilical cord mesenchymal stem cell exosomes in preventing and treating steroid-induced necrosis of the femoral head in rats. [Methods]：Rats were divided into three groups (n=36): (A) blank control group; (B) Model group: rats were intramuscular injected with methylprednisolone (20 mg/kg) to establish steroid-induced femoral head necrosis model in rats; (C) Exosomes group: Rats were injected with exosomes 2 hours before intramuscular injection of methylprednisolone through the tail vein (1×1010/mL). HE staining, Micro CT and TUNEL staining were used to further analyze the effect of human umbilical cord mesenchymal stem cell exosomes on steroid-induced femoral head necrosis in rats safety and efficacy. [Results]: There were statistically significant differences in six indicators among the three groups (P values <0.001), and pairwise comparison was further conducted. Compared with blank control group, the rate of empty bone lacunae, apoptosis rate of osteoblasts and trabecular space (Tb.Sp) in model group were significantly increased (P values <0.001), and the model group showed that the internal structure of the femoral head was disordered, the trabecular bone was broken, and the arrangement was disordered.. Compared with model group, the rate of bone lacunae, apoptosis rate of osteoblasts and trabecular space (Tb.Sp) in exosome group were decreased (P values <0.001). The bone volume fraction (BV/TV), trabecular thickness (Tb.Th), and trabecular number (Tb.N) were all increased (P<0.001、P = 0.003、P = 0.001). [Conclusion] : Human umbilical cord mesenchymal stem cell exosomes can prevent glucocorticoid-induced steroid-induced femoral head necrosis in rats, which may be related to the inhibition of osteoblast apoptosis.