Fast　acquisition　of　the　integral　tooth　surface　data　is　significant　in　the　quality　evaluation　of　gears.　The　line　laser　measurement　provides　an　efficient　solution　to　acquire　the　above　data,　but　its　measurement　accuracy　remains　to　be　improved.　A　too　large　incident　angle　of　measuring　light　seriously　affects　the　integrity　of　the　obtained　tooth　surface　data,　thus　limiting　the　extraction　of　effective　tooth　surface　and　the　quality　evaluation　of　tooth　surface.　In　order　to　clarify　the　influences　of　incident　angle　of　measuring　light　on　the　acquired　tooth　surface　data　in　the　gear　measurement,　taking　a　cylindrical　gear　as　an　example,　a　mathematical　model　of　incident　angle　is　established.　It　is　verified　by　simulation　analysis　and　five　groups　of　measuring　experiments.　Based　on　the　simulation　results　and　experimental　data,　the　influences　of　offset　and　inclination　angle　of　the　laser　sensor　on　the　incident　angle　of　measuring　light　are　further　analyzed.　The　incident　angle　decreases　significantly　with　the　increase　in　the　offset.　The　influence　of　the　inclination　angle　smaller　than　60.　on　the　incident　angle　is　insignificant　and　could　be　ignored.　In　addition,　according　to　the　types　of　gears,　the　reasonable　position　and　attitude　of　the　sensor　are　determined　to　reduce　the　influence　of　the　incident　angle　of　measuring　light　on　measurement　accuracy.