Purpose: Recently, the performance of the X-ray tube was very much improved by the power generation of the technology. However, the overload of equipment is occurred by the increment of the equipment operating time according to the increment of the examination number of cases. The X-ray dose can change by heat occurrence of the X-ray tube due to this. Moreover, the change of the bone mineral density value is possible to occur. Therefore, We tries to whether the change of the bone mineral density value of each equipment according to the difference of the examination number of cases and operating time occur or not. Materials and Methods: The BMD value was measured by the Aluminum Spine Phantom and the European Spine Phantom in each equipment, in order to find out about the difference of the time general classification bone mineral density value by using the Dual energy X-ray absorptiometry. And after scanning each phantom by using X-ray dose meter (Unfors Mult-O-Meter), a dose was measured by the same condition. As to, an average and standard deviation were found and the change of each equipment much BMD value was compared and it evaluated. Results: $Mean{pm}SD$ of each equipment by using the Aluminum Spine Phantom, A equipment was $1.174{pm}0.002$, $1.171{pm}0.005$, $1.173{pm}0.005$, B equipment was $1.186{pm}0.003$, $1.187{pm}0.003$, $1.185{pm}0.003$, C equipment was $1.180{pm}0.003$, $1.182{pm}0.004$, $1.183{pm}0.002$, D equipment was $1.188{pm}0.004$, $1.185{pm}0.003$, $1.185{pm}0.004$. By using the European Spine Phantom, A equipment was $1.143{pm}0.006$, $1.153{pm}0.009$, $1.161{pm}0.003$, B equipment was $1.134{pm}0.004$, $1.13{pm}0.008$, $1.127{pm}0.015$, C equipment was $1.143{pm}0.006$, $1.134{pm}0.01$, $1.133{pm}0.006$, D equipment was $1.14{pm}0.001$, $1.122{pm}0.002$, $1.131{pm}0.008$, altogether included in the normal range. Conclusion: There was no significant change of the BMD value of using a phantom by time zones. Therefore, if the quality control is made to use the extent management method of the equipment for beginning in the present application, the reliability of the BMD equipment will be able to be enhanced.