It　is　more　difficult　to　measure　a　fine-pitch　gear　than　a　medium　pitch　gear　because　of　the　effect　of　geometrical　dimension　and　mechanical　performance.　With　technical　development,　the　dimension　of　a　fine-pitch　gear　is　getting　smaller　and　smaller　but　the　precision　is　becoming　higher　and　higher,　especially　due　to　Micro-gear＇s　appearance.　It　leads　to　a　new　challenge　to　measure　a　fine-pitch　gear.　Adopting　traditional　measurement　methods,　the　analytic　measurement　for　gears　can　not　reach　0.2　mm　and　the　functional　measurement　for　gears　can　not　reach　0.1　mm.　Owing　to　the　strict　limitations　of　gear　diameter,　gear　single-flank　rolling　test　can　not　attract　the　attention　which　they　should　be　deserved.　It　can　be　said　that　the　traditional　measurement　methods　have　been　unable　to　meet　small　modulus　gear　measurement　requirements.　So　the　technology　of　fine　pitch　gear　measurement　has　become　a　hot　research　in　recent　years.　Currently,　the　technology　of　fine-pitch　gear　measurement　shows　new　development　trends,　such　as　the　gear　parallel　measuring　technology　based　on　the　optics;　the　gear　analytic　measuring　technology　based　on　the　optical　fiber　probe　and　gear　single　flank　rolling　test.