Abstract: 【Objective】To study the restraining effect of Glycyrrhizin(GL),a Chinese medicine,on Staphylococcus aureus-induced mastitis in mice. 【Method】Thirty pregnant BALB/C mice randomly divided into nomal control group(Con,n=10)、positive control group(P,n=10) and treatment group (T,n=10). Either sterile physiological saline solution(PSS) or 50μl 7.0×102CFU Staphylococcus aureus was inoculated into the fourth abdominal mammary gland via the teatduct 8-10d after parturition. Either 88mg/kg Glycyrrhizin or PSS 0.2ml was injected into abdominal cavity after inoculated -12h、0h、12h、36h. Exactly 66 h after inoculation,the mice were euthanatized and the mammary glands were removed and fixed for histopathologic evaluations. 【Results】Histopathologic examination of mammary gland revealed that the mammary glands of positive control group had more severe pathologic lesion than those of the treatment group. There was significant increase (p＜0.01) of the interstitial width in mammary gland of positive group and treatment group compared with those of nomal control group,but decreased (p＜0.01) of the interstitial width in mammary gland of treatment group compared with positive control group.Compared with nomal control group, Tumor Necrosis Factor-α(TNF-α)、Interleukin-γ (IFN-γ) concentration increased remarkably in mammary gland of the positive control group. There was significant decrease (p＜0.01) of TNF-α and IFN-γ concentration in mammary gland of treatment group compared with those of positive control group. 【Conclusion】 The results demonstrate that Colony For Units(CFU)、tissue scathe、inflammation and body reactions were mitigated and mammary gland was protected by Glycyrrhizin.