With age, bone loss in middle-aged and elderly people is in negative equilibrium in bone reconstruction, the mechanism of which is due to increased resorption of osteoclasts on the one hand; on the other hand, it is due to the attenuation of osteoblast function leading to a decrease in bone mass, which is the cytological basis of osteoporosis. The factors that cause bone loss in middle-aged and elderly people are very complex, and recent studies have concluded that they are closely related to the following factors. (1) The reduction of sex hormone secretion in middle and old people is one of the important causes of osteoporosis: it is a recognized fact that estrogen level decreases after menopause, resulting in increased bone resorption. Androgens are also one of the important hormones regulating bone metabolism. Androgens have a role in promoting protein synthesis and have a role in promoting the synthesis of bone matrix. It has been reported at home and abroad that bone mineral loss in middle-aged and elderly people is negatively correlated with serum sex hormone level. (2) Dysregulation of calcium-regulating hormone secretion with age leads to disorders of bone metabolism: There are three calcium-regulating hormones in human body, namely calcitonin (CT), parathyroid hormone (PTH) and 1,25(OH)2D3. CT is secreted by thyroid “C cells”, which can reduce bone conversion, inhibit bone resorption and promote bone formation. 1,25(OH)2D3 promotes the absorption and utilization of calcium. Significantly reduced renal function and reduced creatinine clearance in the elderly leads to increased blood phosphorus, which secondary to increased PTH, increased bone resorption and decreased bone calcium. The decrease in 1α hydroxylase activity in the kidneys of the elderly leads to a decrease in 1,25(OH)2D3 synthesis, a decrease in intestinal calcium absorption, and a feedback increase in PTH secretion. C-cell” function declines in the elderly, CT secretion decreases, and bone formation decreases. (3) The elderly have a lack of protein, calcium, phosphorus, vitamins and trace elements due to the loss of teeth and lower digestive function, poor bone nano, and low intake of good nutrition: research shows that insufficient or excessive protein intake has a negative regulatory effect on calcium balance and bone calcium content. Our customary diet is low calcium recipes, calcium sources mainly rely on cereals and vegetables, the elderly have more missing teeth, vegetables, fruits, lean meat is not easy to chew, the intake is reduced, showing a “negative calcium balance”, feedback PTH secretion rise, mobilization of bone calcium dissolution, blood calcium rise. The blood phosphorus level is significantly negatively correlated with age, and the Ca/P ratio increases in the elderly due to the decrease in blood phosphorus, leading to a decrease in osteogenesis. Vitamin K deficiency can affect the carboxylation of osteocalcin, and the elevation of uncarboxylated osteocalcin can accelerate bone loss and predispose to fracture. (4) As we age, outdoor exercise decreases is also an important reason why the elderly are susceptible to osteoporosis:Studies have shown that institutional loading can increase the bone conversion rate, stimulate osteoblast bioactivity, and increase bone reconstruction and bone mass accumulation. Long-term adherence to regular weight-bearing walking or running or stair climbing can increase the BMD of the vertebral body. Regardless of age, as long as long-term adherence to physical exercise and in vivo labor is maintained, the loss of mineral volume due to ageing can be reduced. The elderly after surgery or serious diseases such as myocardial infarction, stroke, etc., especially to avoid long-term absolute bed rest, advocate early out of bed activities. It has been studied that if the bone mineral signal of the lumbar spine is reduced by 0.9% for one week in bed, and if the bone mineral content is reduced by 30%, fractures are very likely to occur. Older people have limited mobility, outdoor exercise and sunlight reduction, so that vitamin D synthesis is reduced, the content of 25 (OH) 2D3 in the blood of older people over 60 years of age is 30% lower than that of young people aged 20 years, vitamin D sustenance can make the intestinal calcium and phosphorus absorption decline, so that bone formation and bone mineralization is reduced. (5) Recent studies in molecular biology have shown that osteoporosis is closely related to vitamin D receptor (VDR) gene variants:BMD is reduced in the pure-sibling BBAA genotype. If early prevention and treatment measures are taken for this high-risk group, it is important to prevent primary osteoporosis. Yasuhiro Takeuchi, a Japanese scholar, studied the etiology of osteoporosis in the elderly and concluded that a decrease in transforming growth factor beta (TGF-β) in the bone matrix is likely to be responsible for the decrease in bone formation capacity.