Objective:To observe the clinical efficacy of modified Gualou Niubang Decoction in the treatment of early-stage acute mastitis during lactation. MethodsSixty subjects of early-stage acute mastitis during lactation were randomly divided into the treatment group and control group,30 cases in each group. The treatment group was treated with modified Gualou Niubang Decoction and the control group was treated with intravenous infusion of penicillin,both groups were received the manual massage to drain milk,with a course of 6 days. The clinical efficacy was observed and the time for defervesce and pain and lump disappearance and the adverse reactions were compared.  Results:①The total effective rate of the treatment group and the control group were 96.67% and 100% respectively. There was no statistically significant difference on the clinical efficacy between the two groups,and the effect of the treatment group was similar to the control group(P>0.05). ②There was no statistically significant difference on the time for defervesce between the two groups(P>0.05)；there were statistically significant differences on the time for pain and lump disappearance between the two groups(P<0.05),which suggested that the relief of some symptoms in the treatment was faster than that in the control group. ③There was no statistically significant difference on the incidence of adverse reactions between the two groups(P>0.05).  Conclusion: The effects of modified Gualou Niubang Decoction in the treatment of early-stage acute mastitis during lactation may be equivalent to antibiotics,but it may be faster to relieve pain and lump.