Common causes of weakness on one side of the body include spinal cord lesions, cerebrovascular diseases and intracranial organic lesions. 1. Spinal cord lesions: If the spinal cord has lesions, such as compressive myelopathy, it can cause weakness and sensory impairment on one side of the body. 2. Cerebrovascular disease: Cerebral infarction, transient ischemic attack and cerebral hemorrhage may cause weakness on one side of the body, and may be accompanied by other symptoms such as sensory impairment and hemianopsia. 3. Intracranial organic lesions: Intracranial organic lesions such as brain tumor, cerebral aneurysm or cerebral vascular malformation may also lead to weakness on one side of the body. If you feel weak on one side of your body, you should go to regular hospitals in time to find out the cause of the disease and carry out symptomatic treatment under the guidance of professional doctors.