Abstract: The orderly change of yin and yang hexagrams in Zhouyi shows the cycle rule of time rhythm and the principle of life evolution. The basic principle of the mutual rooting of yin and yang, mutual opposition of yin and yang, combined with yin-yang balance constructs the theoretical core of time rhythm. Professor Xia Gui-cheng believes that the female menstrual cycle presents a circular movement of the biological clock rhythm, and the growth and decline of yin and yang is throughout the menstrual cycle. The change of the menstrual cycle is related to the rhythm of day and night, four seasons, or solar terms, which is consistent with the waxing and waning phases of the moon. Therefore, he advocates that in the treatment of irregular menstruation, we should grasp the rules of time phases and yin-yang changes. Specifically, we should adjust yin and yang according to the rhythm of day and night, regulate qi and blood according to the rhythm of the moon phase, and tonify the kidneys according to the rhythm of the four seasons. Professor Xia Gui-cheng founded the theory of regulating menstruation of gynecology in Chinese medicine, which provides clinical ideas for the regulation and treatment of irregular menstrual disorders and related gynecological problems.