In daily life, people often confuse Parkinson’s disease with dementia (especially Alzheimer’s disease). Although both Parkinson’s disease and Alzheimer’s disease occur in old age, there is a clear difference between the two in terms of clinical manifestations, pathogenesis and treatment. In terms of symptoms, the main manifestation of Alzheimer’s disease is forgetting recent events, and the main symptoms of Parkinson’s disease are muscle stiffness, hand tremor, and slow movements; Parkinson’s patients have normal intelligence and memory; Alzheimer’s patients are often paranoid, and Parkinson’s patients are often accompanied by depression. Early Parkinson’s patients rarely develop dementia, but there are 30-40% of patients will be combined with the occurrence of dementia in the late stage, foreign research found that the probability of Parkinson’s patients to develop dementia is roughly 6 times that of normal people, Parkinson’s disease lesions in the late stage of the cerebral cortex, the limbic lobe system of the brain cell death, may be the main cause of dementia.