A whole human lumbar spine was used as experimental specimen,the parallel light 3-D movement measurement system was designed and applied, then 3-D movement parameter of Special point of lumbar spine posterior elements was obtained during varying movement.By means of an analysis of loading-displacement curve,we found regularity in the stereoscopic movement of important region of lumber spine posterior elements. During right rotation the relative motion of right L_4 inferior process of facet joint were 0.6mm (backward)1.0mm(upward) and 3.0mm (right lateralward), it resulted in enlarging the volume of L_5 nerve root canal.While flexional,no matter which lumber spinal section it is,the motion is foreward and upward with a little lateral displacement.The main movement axis of different segment of aged lumbar spine specimen changed not regularly in X and Z axes,the displacement variable were more large than that of young and middle age specimen in loading,due to degeneration and stability of specimen.