Patients with numbness on the left side of the face may be the precursor of thrombosis, or it may be the precursor of plant nerve dysfunction or facial neuritis. It is recommended that patients promptly consult the neurology department of the hospital for examination. First, if the patient is a middle-aged or elderly person with risk factors of cerebral atherosclerosis and cerebral thrombosis and suddenly develops numbness on one side of the face, accompanied by tongue extension, salivation at the corners of the mouth or numbness and unfavorable movement of the upper limbs, it is considered to be caused by cerebral thrombosis. Secondly, if the patient does not have risk factors for cerebrovascular disease, but feels numbness on the left side of the face under the condition of emotional anxiety, depression and poor sleep, and there is a clear cause, it may be a manifestation of neurosis, which is a disorder of plant nerve function. In the third aspect, if the patient’s numbness on the left side of the face occurs under the condition of being cold or wind-blown, accompanied by shallow frontal lines, it is considered to be caused by facial neuritis.