BACKGROUND:　Unilateral　external　fixators　are　widely　used　in　orthopedics　to　stabilize　fractured　bones　and　in　the　treatment　of　limb　deformities.　The　main　value　for　evaluation　of　mechanical　stability　of　the　external　fixator　is　fixator　stiffness.　The　fixator　stiffness　is　an　important　factor　as　it　will　influence　the　biomechanical　environment　to　which　fixator　and　regenerating　tissues　are　exposed.　OBJECTIVE:　The　main　objective　of　this　work　was　to　monitor　the　transmission　of　stress　and　the　change　of　displacement　generated　in　fixator-bone　system　under　three　loading　conditions　during　healing　process.　METHODS:　In　this　study,　a　finite　element　model　with　changing　Young＇s　modulus　of　the　callus　is　established,　finite　element　analysis　was　used　to　investigating　stress　and　deformation　of　fixator-bone　system　caused　by　axial　load,　torsional　load　and　bending　load　during　three　healing　stages.　RESULTS:　The　results　reveal　that　at　different　healing　stages,　stress　distribution　between　the　fixator　and　fractured　bone　is　different,　the　position　of　displacement　is　mainly　concentrated　in　the　fracture　site　and　proximal　bone　and　with　the　increase　of　healing　time,　the　deformation　decreased.　CONCLUSIONS:　This　work　helps　orthopedic　doctors　to　monitor　the　progression　of　fracture　healing　and　determine　the　appropriate　time　for　removal　of　a　fixation　device　and　provide　useful　information.