Alzheimer’s disease is a primary degenerative encephalopathy that occurs in old age and pre-geriatric period. Patients have impairment in memory, thinking, analysis and judgment, visual-spatial recognition, emotion and life ability, which affects the quality of life and life expectancy. The prevention of Alzheimer’s disease has the following aspects: 1. balanced diet. The activity of nerve cells in the brain requires sufficient protein, calories, lecithin, choline, vitamins and trace elements, etc. On top of that, attention should be paid to supplementing various necessary nutritional elements. The elderly should eat walnuts, pecans and other dried fruits, more vegetables, cereals, beans, more sea fish and shellfish, while limiting the intake of red meat, using olive oil instead of butter, these habits are beneficial to improve memory and delay the decline of cognitive function. 2, diligent use of the brain. Regular thinking and brain movement can help protect the brain’s acuity, promote blood circulation in the brain and reduce the risk of dementia, so the elderly should actively use their brains to prevent brain decline, such as playing board games, reading, or speaking their thoughts while watching TV or reading can achieve the purpose of brain activity. 3, maintain good social activities. After entering old age, most elderly people have a sense of loneliness, some even closed doors, completely isolated from the outside world, which will accelerate the decline of brain function. Therefore, the elderly should actively get out of the house and enjoy nature; actively participate in various forms of social activities, attend parties, communicate with people and discuss problems, which can also slow down the decline of brain function. 4.Moderate exercise. Moderate exercise can ensure the fitness of the body and improve the immunity. For the elderly, often doing some complex and delicate handicrafts will promote brain activity, such as cooking, writing diary, playing musical instruments, painting, etc. have the effect of preventing dementia. However, exercise should be moderate, pay attention to avoid falls, and senior citizens should use crutches if necessary. 5, maintain a good state of mind. Older people often have to face the experience of loss such as retirement and death of friends, so they should pay attention to adjust their mindset, avoid being too negative and sighing, and live with a cheerful mood. Therefore, dementia is a disease that occurs in the elderly. A reasonable diet, brain exercise, normal social interaction, moderate exercise and maintaining a good attitude can reduce the risk of dementia.