The　clamping　force　of　the　bolted　joint　is　a　key　factor　in　maintaining　its　service　performance.　However,　when　the　torque　wrench　is　removed　after　tightening,　there　will　always　be　a　certain　degree　of　loss　in　the　pre-tightening　force.　Herein,　the　stress　state　of　the　bolt　and　the　nut　during　tightening　and　service　was　analyzed.　The　repeatability　experiment　of　the　threaded　fasteners　during　repeated　tightening　was　carried　out　to　investigate　the　pre-tightening　force　loss　after　the　removal　of　torque　wrench　(initial　loss)　and　the　pre-tightening　force　loss　in　a　period　of　service　(service　loss).　Different　forms　of　lubrication　was　considered,　namely　without　lubrication,　thread　lubrication　and　nut　surface　lubrication.　The　influence　of　the　pre-tightening　force,　repeated　tightening　and　lubrication　on　the　initial　loss　and　the　service　loss　was　analyzed　according　to　the　experimental　results.　It　showed　that　the　pre-tightening　force　and　its　loss　have　a　large　dispersion.　At　the　first　tightening,　the　pre-tightening　force　may　increase　after　the　initial　loss　stage.　When　the　lubricant　is　used,　the　service　loss　has　a　significant　positive　correlation　with　its　pre-tightening　force.　The　use　of　lubricant　at　the　threads　is　easier　to　lead　the　service　loss　of　pre-tightening　force.