To explore the effect of Yanghe Decoction on the expression of CD90 and its antitumor effect in nude mice bearing human breast cancer. Methods:The breast cancer cells were injected into the fourth mammary fat pads of nude mice， establishing the model of nude mice bearing human breast cancer. Then the mice were randomly divided into 5 groups: blank control group, cyclophosphamide group, Yanghe Decoction low dose group, middle dose group and high dose group. After 14 days inoculation, model mice were administered, tumors were collected after 2 weeks. Tumor weight and expression of CD90 were measured. Results: With regards to expression of CD90 and tumor volume and weight, cyclophosphamide group and Yanghe all dose groups were statistically lower than those of the blank control group (P<0.05), but there was no significant differences between the cyclophosphamide group and Yanghe dose groups (P>0.05). The positive expression rate of cyclophosphamide group, low, middle, high dose groups were 0.34%, 0.73%, 0.52% and 0.42%; the tumor inhibition rates were 63.64%, 37.45%, 47.64% and 63.27%. Conclusion: Yanghe Decoction can obviously inhibit the growth of human breast cancer cells and down-regulate CD90 in human breast cancer tissue, which may be one of the mechanisms of breast cancer inhibition.