Abstract: The paper discussed the waxing and waning of essence-yin and essence-yang rules in menstrual cycle rhythm and the treatment thought of related diseases. Based on the theory of Yi, Professor Xia Guicheng proposed the concept of essence-yin and essence-yang in the female reproductive physiological system, which elaborated its material basis, zang-fu regulation and its function on the rehabilitation of menstrual cycle. Combined with the further analysis of gynecological diseases, Professor Xia Guicheng considered that the menstrual cycle rhythm was equal to the change rule of the female reproductive physiological system, the treatment thought should base on the modern disease spectrum to extend the application of traditional Chinese medicine theories in gynecology.