Objective:To compare the effects on stress distribution of internal fixators of lumbar vertebra by using bone graft in intervertebral slot,and to provide the mechanical gist to reduce the fatigue made by intemal fixators of lumbar vertebra during clinical application.Methods:Six fresh samples of human lumbar vertebras were used to make models of unstabilized lumbar(vertebrate burst injury model)by transplanting the universal spine system.Stress of fixators of the universal spine system after remaining intervertebral disc,removing part of intervertebral disc and grafting bone in intervertebral slot were measured respectively and compare analysis of stress distribution of the internal fixators under three condition were made.