Abstract: This paper firstly expounds the origin and theoretical connotation of Opening and Closing Pivot Theory,and then the special physiological process of women's perimenopause from the perspective of this theory. Considering that the abnormal ascending and descending of the opening and closing pivot may lead to menopausal syndrome (MPS),this paper further explores its mechanism. It is concluded that the abnormal yin pivot of shaoyin and closing of the liver of jueyin are the basis of MPS,and the abnormal yang pivot of shaoyang and opening of the spleen of taiyin are the inducement of MPS. Insomnia is a prominent symptom of MPS, and the main reason of it is the abnormal qi transformation of one kind of yang and three kinds of yin from the Opening and Closing Pivot Theory. This paper finally expounds the pathogenesis of Chaihu Guizhi Ganjiang Decoction in treating MPS combination with "six-channel diseases tending to be cured" from the aspect of this theory.