Objective: To observe the effect of Ruxiankang (RXK) Capsule (Radix Bupleuri, Poria, Rhizoma Atractylodis macrocephalae, Radix Angelicae Sinensis, Radix Paeoniae Alba, Rhizoma Cyperi, etc.) on mammary gland and sex hormone of rat with mastoplasia. Methods: After benzoate estradiol and progestogen were injected into rats for 30 days the mastoplasia model was made, the model rats were treated with tamoxifen and RXK Capsule for 30days, and injected estradiol at the same time. Results: RXK Capsule and tamoxifen could significantly inhibit HMG rat's mammary gland swell, reduce quantity of lobule alveolus in mammary glands and secretion ( P