The accurate measurement for a long bone have taken an important part in orthopedics surgical diseases when the length of extremities is different each other. However, it is true that various kinds of methods to search for the accurate measurement on used in medical centers. In this study, we measured the real length of long bone for CT Scanogram and F.F.D by 100cm and 200cm in the angle of inclination $0^{circ},;3^{circ}$ and $7^{circ}$. This method will be useful to diagnose and treat patients more accurately.