The decrease of bone mimeral density(BMD) after fracture is a well known phenomenon. Several studies of the changes of BMD after fracture demonstrated decrease of bone density not only at the fracture site, but also along the whole fractured bone. An accurate and precise quantification of BMD is necessary to determine the onset, the rate of progression, and the extent of the demineralizing process. THe change of BMD was studied during the fracture healing period of long bones in patients with fractures of the lower limbs using the Dual Energy X-ray Absorptiometry (DEXA). The Dexa was used to measure BMD of the fracture site, and proximal and distal fragment of fractured bone. BMD in the three measuring was checked on 10, 20, 30, 40, 60, 120 days after operation. The results of this study were as follows: 1. A progressive decease of BMD was observed not only at the fracture site, but also at the proximal and distal segment to the fracture site until 4 months after operation. 2. The above phenomenon was well demonstrated during the fracture healing process and callus formation period. 3. The range of motion and partial weight bearing did not affect the progression of BMD change in the early postoperative period.