The main reasons for the occurrence of osteoporosis in the elderly are: first, the reduction of sex hormone levels in the body. The insufficient level of sex hormones disrupts the dynamic balance between bone formation and bone decomposition process, which slows down the deposition of blood calcium into bones and accelerates the process of transforming bones into blood calcium, resulting in osteoporosis in old age. In this process, the influence of estrogen on bones is more obvious, so osteoporosis is more obvious in old women after menopause. The second is the reduced intake of calcium. The dietary structure of the elderly changes, the gastrointestinal function decreases, the absorption function decreases, so that the absorption of calcium in the body decreases, while the excretion in the body remains the same or increases slightly, thus causing the lack of calcium in the body. The third is the deficiency of vitamin D. Changes in the diet of the elderly and the reduction of outdoor activities make the source and transformation of vitamin D present a deficiency, which can contribute to the occurrence of osteoporosis. The fourth is a decrease in physical activity. Under a certain stress, the density of bones will increase, the thickness of bone tissue and the density, quantity and quality of bone trabeculae will increase, while the elderly will have significantly less exercise and a significant decrease in strength, which will reduce the stress bones are subjected to, thus causing the bones to develop disuse osteoporosis. Other causes, such as individual differences, dietary habits, physical condition, disease, race, and even geography, are associated with the development and progression of osteoporosis.