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 their quality of life and life expectancy. The prevention of Alzheimer’s disease mainly includes the following aspects: a. Balanced diet: The activity of nerve cells in the brain requires sufficient protein, calories, lecithin, choline, vitamins, trace elements and so on. Older people can eat walnuts, pecans and other dried fruits, more vegetables, cereals and beans, usually eat more sea fish and watery shellfish, limit the intake of red meat, use olive oil instead of butter, these habits are beneficial to the improvement of memory and delayed cognitive decline. Two, diligent brain: regular brain thinking can help protect the brain’s acuity, promote the brain’s blood circulation, reduce the risk of dementia, the elderly should actively use their brains to prevent brain decline, such as playing board games, reading, or watching TV, reading their thoughts, can achieve the purpose of brain activity. Third, maintain good social activities: after entering old age, many 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. Fourth, moderate exercise: moderate exercise can ensure the fitness of the body and improve 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 to avoid falls. Fifth, maintain a good state of mind: the elderly often have to face the experience of retirement, the death of friends and other loss, should pay attention to adjust their mindset, avoid too negative, sighing, to live in a cheerful mood. As mentioned above, dementia is a disease that occurs in the elderly, but a reasonable diet, brain exercise, normal social life, moderate exercise and a good attitude can reduce the risk of dementia. Since Alzheimer’s disease is insidious in its onset, early detection and prevention is the most important thing to do.