Abstract: Establishing an human spine dynamic model is an significan event to study spine injured biomechanics of pilot's ejective injury,parachute opening,landing and study the endurance to impact loading on human spine.In this paper,the Huston's method of Kane's equations is developed so that it can be applied to the multi body system including translation between the bodyies.The dynamic model of human spine is provided basing on these theories,while the big movement of spine is considered.The deformation of vetebra is far smaller comparing with the intervetebra disc,so the spine is considered into multi body system including rigid bodies (vetebra) and the flexible bodies (intervetebra disc).The computer solution correspond with the results of the large scale human impact test.The rigid coefficient factors and the damping factor of intervetebra joints are obtained.