RV　reducer　is　an　important　function　part　of　industrial　robot　joints.　The　cycloid　gear　measuring　problem　is　the　key　part　of　high　precision　RV　reducer　manufacturing.　A　brief　introduction　to　the　forming　principle　and　formulas　of　RV　reducer　cycloid　tooth　contour.　A　new　method　for　measuring　the　contour　accuracy　of　RV　reducer　cycloid　gear　is　proposed　in　the　paper,　which　is　used　coordinate　measuring　machine　to　detect　the　tooth　contour　error　of　cycloid　gear.　The　measuring　method,　steps　and　precautions　in　measuring　are　discussed　in　detail.　Proposing　a　data　processing　and　verification　program　and　the　cycloid　gear　manufacturing　error　is　also　analyzed.　The　detection　method　is　certified　to　meet　the　application　requirements　through　actual　measurement.