To observe the efficacy of the yin-nourishing and heat- clearing therapy on Polycystic ovary syndrome (PCOS) with pattern of internal heat due to yin deficiency. Methods:Sixty patients with PCOS were randomly divided into treatment group (n=30 ) and control groups(n=30). Patients in treatment group received Ziyin Tiaoxue decoction twice daily，given orally for 25 days, and patients in treatment group received Diane-35 for 21days. The 2 groups were treated for 3 menstrual cycles. Menstruation (includes menstrual cycle, days, amount and texture of menses), gestation, acne, polycystic ovaries and LH/FSH of the 2 groups were evaluated before and after treatment. Results: After 3 menstrual cycles of treatment, there was a significant difference in the resume of regular menstruation, pregnancy rate and improvement of polycystic ovaries between the two groups (P<0.05). The reduction rate of acne was 92.3% in treatment group and 90.91% in control group (P<0.05). All the level of LH/FSH of the 2 groups were lowered after the treatment （P<0.05）, but it has no significant difference among the 2 groups（P>0.05）. Conclusion: The yin-nourishing and heat- clearing therapy is effective for PCOS caused by deficiency of liver and kidney and pattern of internal heat due to yin deficiency. It can resume menstruation, restore ovulation, relieve acne and promote pregnancy rate. In addition, Ziyin Tiaoxue decoction has greater safety and no adverse reactions.