Abstract: Objective:To investigate image characters and diagnostic value of X-ray,CT and MRI films on lumbar degenerative instability.Methods: The image characters of X-ray film,CT and MRI in 154 cases with lumbar degenerative instability were analyzed retrospectively.All of cases with lumbar degenerative instability were confirmed by operation.The diagnosis reference of lumbar degenerative instability primary based on lateral position（LP） films of lumbar hyperextension and hyperflexion position.When lumbar vertebral anterior slipped over 4 mm or segmental angulation exceeded 15 on lumbar sagittal translation were considered significance.The lumbar degenerative instability diagnosis standard secondly based on image characters of anterior-posterior（AP） position,LP,CT and MRI films.Results:According diagnosis reference,typical changing showed in 105 cases（67%） on AP position films,111 cases（72%） on LP films,146 cases（95%） on dynamical position films and 46 cases（30%） on bi-oblique position films.The cases with CT and MRI examination were found diversity lumbar degenerative changing on films.Conclusion:The diagnosis of lumbar degenerative instability chiefly bases on the hyperflexion and hyperextension films.The typical changes of X-ray,CT and MRI were extremely important for diagnosis of lumbar degenerative instability.