Abstract: Due to the serious increasing of osteoporosis, how to obtain accurate bone mineral density has arouse greater attention all over the world. With the development of medical technology, dual energy X-ray absorptiometry is widely applied in the diagnosis of osteoporosis because of its accuracy, low dose and variety. In this paper, we state the concept of bone mineral density, and summarize the methods and the sites of measurement in clinical diagnose of osteoporosis. It focuses on the fundamentals of dual energy X-ray absorptiometry, explores in great depth the key techniques, and elaborates current problems and limitation in both hard ware and software. Accordingly, this paper also discusses and predicts the future development tendency of dual energy X-ray absorptiometry's future development and improvement.