Abstract: The theory of manifestation, root cause and medial qi constructs a circular motion system of yin and yang ascending and descending, with the six climatic qi as the fundamental, the three yin and three yang as the superficial manifestations, and the intermediate qi as the pivot. This system maintains the dynamic balance of natural and human qi transformation. By interpreting the female reproductive rhythm through the rules of conformity among manifestation, root cause and medial qi, it is proposed that the heart and kidney correspond to sovereign fire of Shaoyin and cold water of Taiyang, while the liver and spleen correspond to Jueyin-Shaoyang and Taiyin-Yangming. This forms a harmonizing system of qi, blood, yin, and yang, centered on the heart and kidney and coordinated by the liver and spleen, which governs female reproduction.From the perspective of this theory, the menstrual cycle is interpreted as follows: the storage function of Taiyang cold water corresponds to the pivot of transitioning from extreme yin to yang during the intermenstrual phase; the free-flowing function of Jueyin-Shaoyang corresponds to the mechanism of yang growth and yin decline during the premenstrual phase; the descending function of Shaoyin sovereign fire corresponds to the transformation from extreme yang to yin during the menstrual phase; and the descending function of Yangming-Taiyin corresponds to the foundation of yin growth and yang decline during the postmenstrual phase. By regulating yin and yang according to the characteristics of each phase and differentiating treatments based on cycle stages, the normal rhythm of the menstrual cycle can be restored. This highlights the insights of traditional theory into gynecological diseases and provides valuable references for further guiding their treatment.