Background: The aim of the present study was to evaluate whether the HMG (Hyperplasia of the Mammary Gland) effect of RuXian-I in estrogen- and progestogen- induced HMG rats is mediated through the activation of MAPK (Mitogen activated protein kinase) and NF-κB signaling pathways. Materials and methods: Fifty virgin female Wistar rats were randomly divided into in control and HMG, RuXian-I (0.75 g·kg⁻¹, 1.5 g·kg⁻¹, 3 g·kg⁻¹, respectively) groups, 10 in each. Injections of estrogen and progestogen were given to establish rat models of HMG and RuXian-I at the same time. Changes in nipple heights were measured; pathologic changes of HMG in rats were also observed under a light microscope; the phosphorylation levels of MAPK and NF κB and the expression levels of TNF-α and IL-1β were measured. Results: Compared with the control group, the nipple diameters and height were increased significantly, the numbers of MG lobules were increased, there were changes in breast histopathology, the levels of TNF-α and IL-1β increased significantly, and MAPK and NF-κB were activated in HMG rats. Compared with the HMG model group, the increased nipple height was decreased, the numbers of MG lobules were reduced, the degree of HMG in rats was alleviated obviously, and the phosphorylation level of MAPK and NF-κB and cytokines TNF- α and IL-1β levels in serum were decreased by RuXian-I treatment. Conclusion: Those results suggest RuXian-I has protective and therapeutic effects on HMG rats induced by estrogen and progestogen and is likely to activate MAPK and NF-κB signaling pathways.