There are many causes of premenstrual drowsiness, and the common causes are mainly the following. First, insufficient blood supply to the cerebral arteries, premenstrual due to the richer blood flow of pelvic congestion, can cause a reduction in the relative blood supply to the brain, thus causing cerebral ischemia, hypoxia, dizziness, drowsiness and weakness, mental lethargy, etc.. Generally, the symptoms can be relieved after the menstruation without too much treatment. Second, iron deficiency anemia, menstruation due to the large amount of bleeding can cause a decrease in peripheral blood red blood cells, the body’s oxygen-carrying capacity is not enough, which leads to pale face, mental lethargy, drowsiness and weakness, etc.. The diagnosis can be clarified by perfecting routine blood tests, and severe cases can be treated symptomatically with ferrous sulfate. Third, the plant nervous disorder, mostly seen in menopausal women. The clinical manifestations are various, mainly dizziness, headache, drowsiness and weakness, memory loss, inattentiveness, etc. The symptoms can be improved by taking drugs such as glutamate and acetic acid to regulate the disorder of plant nerves.