Visual　measurement　is　one　of　the　important　measurement　methods　for　pinion　gears.　The　measurement　principle　and　the　systematic　structure　of　a　pinion　gear　visual　measuring　system　were　given.　Pixel　equivalent　is　the　key　parameter　in　the　visual　measurement　system,　which　needs　to　be　calibrated　before　dimensions　evaluation.　A　glass　dot　calibration　plate　was　applied　in　the　system　calibration.　Pixel　equivalent　calibration　experiment,　LED　brightness　experiment,　edge　compensation　experiment　and　multiposition　edge　compensation　experiment　was　carried　out.　The　parameter　pixel　equivalent　is　determined　by　the　comparison　between　the　physical　size　of　center　distance　of　adjacent　mark　circle　in　the　glass　dot　calibration　plate　and　its　pixels　number　obtained　by　the　visual　system.　The　center　distance　of　adjacent　mark　circle　was　chosen　to　avoid　the　affection　of　the　brightness　of　light　source　and　the　sub-pixel　technology　was　used.　The　proper　brightness　condition　of　LED　light　was　selected　in　the　LED　brightness　experiment.　Under　this　condition,　the　compensation　of　edge　deviation　was　obtained　by　analyzing　the　edge　position　deviation　in　the　diameter　measurement　of　the　mark　circle　of　the　calibration　plate.　The　experimental　results　show　that　the　pixel　equivalent　is　5.59522μm/Pixel,　and　the　compensation　of　edge　deviation　is　0.54μm.　49　diameters　of　the　circular　marker　were　measured　in　edge　compensation　experiment,　the　largest　difference　between　the　measured　diameter　in　central　vision　after　compensation　and　its　physical　dimensions　is　0.3μm,　which　is　0.2μm　in　muti-position　edge　compensation　experiment.　The　calibration　methods　and　the　experimental　research　are　important　for　the　designed　visual　measurement　system　for　pinion　gears.　Copyright　©　2019　ASME.