Traditional　double-flank　gear　rolling　tester　can　obtain　the　radial　composite　deviations　of　the　gear,　but　it　is　hard　to　obtain　axial　deviations　(helix,　taper,　etc.)　of　the　gear　to　be　measured.　Gear　in-line　measuring　machine　(GMM)　based　on　the　principle　of　double-flank　gear　rolling　inspection　with　many　degrees　of　freedom　solves　the　problem.　This　paper　presents　the　measurement　principle,　axial　deviation　assessing　method,　configuration　and　the　critical　techniques　of　gear　in-line　measuring　machine　(GMM),　which　is　a　new　machine　developed　according　to　the　demand　of　high-speed　inspection　in　mass-production　gear　workshops.　The　strong　feature　of　the　GMM　is　that　the　radial　composite　deviations　and　helical　deviations　of　the　gear　can　be　assessed　in　one　turn　during　high-speed　inspection.