Objective: To investigate the effects of Lirukang oral liquid (LRK, 利乳康口服液) on release of neurotransmitter in rats with hyperpiasia of mammary glands (HMG) and to explore its mechanism. Methods: Sixty rats were divided into six groups, the normal control group, the model control group, the large dosage (3.6g/kg) and the small dosage (1.8g/kg) LRK groups, the Ruzengning (乳增宁, RZN, 2.5g/kg) group and the tamoxifen (TAM, 5mg/kg) group, 10 in each group. Except those in the normal control group, all the animals were made into rat model of HMG by intraperitoneal injection of estradiol benzoate. Levels of dopamine (DA) and 5-hydroxytryptamine (5-HT) in hypothalamus and mammary gland in rats were detected by fluorescence luminosity assay, and level of prolactin (PRL) in serum was detected by radioimmunoassay.Results: In the model group, the level of DA reduced significantly (P＜0.01), and 5-HT and PRL increased obviously ( P＜0.01). Compared with the model group, the LRK groups of both dosages and the TAM group had their level of DA significantly increased (P ＜ 0. 01 ), and level of 5-HT significantly decreased ( P＜0.01). The serum PRL in both LRK groups was significantly decreased ( P＜0.01). No obvious changes in DA, 5-HT and PRL were found in the RZN group. Conclusion: LRK and TAM have similar effects in regulating the release of neurotransmitter in hypothalamus and mammary gland and serum content of estrogen in the animal models of HMG.