In　middle　size　gear　measurement,　the　center　axis　of　the　gear　is　often　used　as　the　measurement　reference.　However,　for　large　gears,　it　is　difficult　to　get　their　center　axis.　In　order　to　overcome　this　difficulty　and　solve　the　profile　measurement　problem　of　super　large　gears,　a　three　dimensional　measurement　and　evaluation　method　is　proposed　in　this　paper.　Firstly,　a　laser　tracker　is　used　to　perform　the　rough　positioning　of　the　gear　under　test,　and　obtain　the　relative　position　relationship　between　the　gear　under　test　and　the　3D　measurement　platform.　Secondly,　plenty　of　data　points　are　acquired　on　the　tooth　surface　of　the　gear　under　test　using　the　designed　3D　measurement　platform,　and　NURBS　surface　fitting　is　conducted　on　these　data　points.　Thus,　the　parametric　model　for　the　real　gear　surface　is　built.　Finally,　the　built　parametric　model　is　compared　with　the　theoretical　model　to　obtain　the　gear　profile　error.　Experiment　results　indicate　that　this　method　has　good　feasibility　in　large　gear　profile　measurement.　©　2016,　Science　Press.　All　right　reserved.