To　realize　on-line　multiaxial　fatigue　damage　evaluation　for　the　servicing　mechanical　components,　a　real-time　multiaxial　cycle　counting　method　is　proposed,　meanwhile,　an　online　multiaxial　fatigue　damage　evaluation　method　based　strain-critical　plane　model　is　given　and　validated　by　the　fatigue　experimental　data　of　En15r　steel.　Investigation　showed　that　the　proposed　on-line　multiaxial　fatigue　damage　evaluation　method　could　provide　satisfactory　evaluation　results,　and　the　real-time　performance　of　the　proposed　cycle　counting　method　is　path-dependent.　©　Published　under　licence　by　IOP　Publishing　Ltd.