Abstract： The theory of "three causes and one change" is a kind of etiology and pathogenesis understanding of fragility fracture proposed by Professor SHI Xiaolin. Professor SHI believes that fragility fracture is closely related to deficiency，stasis and toxin，and they interweaved with each other，which will eventually lead to fragile bone and get broken easily. In the application of the theory of "three causes and one change" to differentiate and treat fragility fracture， doctors should pay attention to supplement its insufficiency in the early stage of the disease. In the middle stage， doctors should additionally adopt the method of treating the branch based on supplementing and boosting， such as invigorating blood and dissolving stasis， and moving qi and dissolving phlegm， and so on. In the late stage， doctors should supplement and boost，and dispel pathogen. In the clinical treatment of osteoporotic fracture，self-made recipe Qianggu Yin is commonly used to differentiate and treat the disease.