Due　to　the　existence　of　redundant　actuation,　the　inverse　dynamics　model　of　the　robot　system　has　an　infinite　set　of　control　torque　solutions　that　can　track　the　desired　trajectory,　which　makes　the　redundantly　actuated　parallel　manipulators　capable　of　completing　additional　tasks　during　operation.　In　order　to　realize　safe　and　precise　operation　of　orthopedic　robot,　a　multi-objective　internal　preload　optimization　method　of　redundantly　actuated　parallel　robots　based　on　variable　impedance　control　is　proposed　in　this　paper.　First,　the　dynamics　of　redundantly　actuated　parallel　manipulator　is　modeled　by　using　the　branch　chain　decomposition　method.　Second,　in　order　to　realize　safe　operation,　a　time-varying　impedance　controller　for　redundantly　actuated　parallel　robot　is　designed,　and　the　stability　of　the　robot　system　is　analyzed　by　using　the　Lyapunov　theory.　On　this　basis,　a　multi-objective　fusion　internal　preload　optimization　method　is　proposed,　which　takes　torque　transmission　performance,　driving　power　and　control　force　as　optimization　objectives,　to　eliminate　the　backlash　during　the　movement　of　redundantly　actuated　parallel　robot.　Finally,　the　effectiveness　of　the　proposed　method　is　verified　through　simulation　experiments　and　comparative　analysis,　and　the　backlash　of　the　robot　system　is　eliminated.　©　2023　Science　Press.　All　rights　reserved.