Objective:　To　systematically　explore　the　change　of　fixator　stiffness　(0.05-7.50　kN/mm)　on　healing　effects　of　seven　different　types　of　fractures　(A1:　simple　spiral,　A2:　simple　oblique,　A3:　simple　transverse;　B2:　wedge　spiral,　B3:　wedge　fragmented;　C2:　complex　segment,　C3:　complex　irregular)　under　the　OTA/AO　fracture　classification.　Methods:　Taking　intramedullary　nail　fixation　of　long　bone　fracture　as　research　objective,　based　on　strain-regulated　tissue　differentiation　theory,　and　combined　with　fuzzy　logic　algorithm　and　finite　element　analysis,　the　process　of　fracture　healing　was　numerically　simulated.　Results:　Moderate　fixator　stiffness　(1.5-2.5　kN/mm)　shortened　the　healing　time　while　ensuring　recovery　of　biomechanical　performance　of　the　fractured　bone.　However,　the　appropriate　fixator　stiffness　corresponding　to　each　fracture　type　was　different.　The　sensitivity　of　healing　effects　to　change　of　fixator　stiffness　was　also　different.　For　type　A　fracture,　when　fixator　stiffness　was　1.5　kN/mm,　optimal　biomechanical　recovery　of　the　fractured　site　could　be　obtained,　while　the　change　in　fixator　stiffness　had　a　large　impact　on　healing　effect.　For　type　B　and　C　fractures,　when　fixator　stiffness　was　above　1.5　kN/mm,　the　change　in　fixator　stiffness　had　no　significant　effects　on　recovery　of　biomechanical　performance.　Conclusions:　Fracture　healing　is　affected　by　both　fixator　stiffness　and　fracture　types.　For　treating　fractures　in　clinic,　the　selection　of　fixators　should　carefully　take　fracture　types　into　account.　Copyright　©　2022　by　the　Editorial　Board　of　Journal　of　Medical　Biomechanics.