To　obtain　the　error　of　gear　characterized　curves　from　gear　topographic　inspection,　a　method　of　gear　profile　orthogonal　distance　regression　was　proposed.　Some　algorithms　involved　in　the　method　were　researched,　such　as　the　matching　of　a　real　gear　profile　with　a　theoretical　gear　profile,　the　calculation　and　decomposition　of　topographic　error　and　the　evaluation　of　profile　character　line　error.　Firstly,　topographic　points　were　obtained　by　coordinate　measurement,　and　the　nonlinear　equation　including　parameters　of　theoretic　profile　was　established.　Then,　the　nonlinear　equation　was　solved　to　get　the　optimal　parameters　of　the　regression　gear　profile　and　to　obtain　the　theoretical　gear　profile　matching　with　the　real　gear　profile.　Here,　the　orthogonal　distances　from　measuring　points　to　the　theoretical　gear　surface　were　calculated　as　the　topographic　errors.　Finally,　based　on　the　multi-degrees　of　freedom　theory　for　gear　deviation,　the　gear　profile　error　and　the　helix　error　were　evaluated　by　local　degree　regression　and　holistic　degree　regression.　The　coordinate　measuring　points　on　a　cylindrical　gear　were　used　as　an　example　for　error　calculation.　The　results　are　well　consistent　with　the　characterized　curves　measurement　using　a　coordinate　measuring　machine,　and　the　difference　is　within　0.5　μm.　These　results　show　that　the　proposed　gear　profile　orthogonal　distance　regression　is　reasonable　and　effective,　and　it　can　be　applied　to　the　gear　inspection　using　coordinate　measuring　machines.　©　2015,　SCIENCE　PRESS.　All　right　reserved.