A method of locating locking holes of an intramedullary nail includes taking an X-ray image of an intramedullary nail having two locking holes； connecting centroids of the locking hole contours and an X-ray source to define locking hole vectors and axial directions of the locking holes； calculating a first included angle and normal vector perpendicular to vectors connecting the X-ray source and the locking hole contour centroids； defining a cross product of the locking hole vector and the normal vector as a vector connecting centers of the locking holes, and calculating second and third included angles with the vector connecting the locking hole centers and the vectors connecting the X-ray source to the locking hole contour centroids； and locating the locking holes according to the first, second and third included angles, vectors connecting the X-ray source to the locking hole contour centroids, and a distance between the locking holes.本發明為骨髓內釘的固定孔之定位方法，對具有二平行固定孔之骨髓內釘拍攝一張X光影像後，藉由固定孔輪廓與X光發射源求出固定孔向量及固定孔之軸向，藉由X光發射源連接至固定孔輪廓之中心點的向量求出第一夾角及法向量，將固定孔向量與法向量外積來定義固定孔中心相連向量，藉由固定孔中心相連向量與X光發射源連接至固定孔輪廓之中心點的向量分別求出第二夾角及第三夾角；藉由X光發射源、第一夾角、第二夾角、第三夾角、X光發射源連接至二固定孔輪廓之中心點的向量及二固定孔的間距求出二固定孔之中心點相對於X光發射源的位置。
