Abstract: This paper discusses the treatment of polycystic ovary syndrome (PCOS) based on the midnight-noon ebb-flow theory. The midnight-noon ebb-flow theory is a Chinese medicine science that combines the time and space of nature with the internal rhythm of the human body. PCOS is characterized by disappearance of the reproductive monthly rhythm. Its etiology is based on kidney deficiency. The key to its pathogenesis is the excess of yin and deficiency of yang, the hyperactivity of yang and deficiency of yin, and the lack of smooth connection between yin and yang. PCOS patients have circadian rhythm disorders, and the oscillation of the core clock gene is attenuated, which leads to the interruption of the circadian rhythm gene in the ovary, the imbalance of yin and yang transformation in the kidney, and the asynchrony of qi and blood flow with the time rhythm. Therefore, the treatment focuses on harmonizing yin and yang and rebuilding the normal reproductive rhythm of women. Using the midnight-noon ebb-flow theory, combined with the reproductive physiological characteristics of women, choosing different drug administration time and selecting meridians and acupoints according to the time will be helpful to unlock the "time code" of the female reproductive system, and assist clinical menstruation regulation, pregnancy and treatment of diseases.