Accurate　force/torque　(F/T)　information　is　essentially　important　for　a　robot　manipulator　to　regulate　the　contact　forces　and　torques　exerted　on　its　tool　(end-effector).　For　a　manipulator　with　mounted　F/T　sensor,　the　tool　and　the　F/T　sensor　are　connected　to　the　manipulator　via　some　components,　of　which　many　parameters　such　as　mounting　errors　and　component＇s　weight　are　unknown.　As　a　result,　the　forces　and　torques　exerted　upon　the　work　point　of　the　tool　of　a　manipulator　is　not　what　directly　sensed　by　the　F/T　sensor,　and　thus　the　F/T　sense　of　the　manipulator　need　to　be　recalibrated　even　though　the　mounted　F/T　sensor　had　been　calibrated　in　advance.　Also　the　unknown　parameters　introduce　challenges　to　the　on-line　recalibration　of　the　F/T　sense　of　the　manipulator.　This　paper　proposes　an　on-line　method　to　calibrate　the　forces/torques　exerted　upon　the　tool　of　a　manipulator　with　wrist-mounted　F/T　sensor.　The　method　can　calibrate　both　of　them　using　only　one　reference　weight　and　without　need　to　dismantle　the　F/T　sensor　and　tool.　It　provides　an　efficient　and　convenient　way　to　calibrate　an　integrated　F/T　system.　Theory　analysis　and　experiment　result　are　presented　to　demonstrate　the　effectiveness　of　the　method.　©　2013　IEEE.