To　lower　the　influence　of　installation　errors　on　gear　pitch　measurement,　an　evaluation　method　of　pitch　deviations　is　introduced,　considering　installation　eccentricity　error　and　installation　wobbling　error.　The　pitch　measurement　points　are　firstly　transformed　from　the　machine　coordinate　system　into　the　workpiece　coordinate　system.　Then　gear　functional　center　is　fitted　according　to　least　squares　equation　established　with　the　pitch　measurement　points　and　base　circle　center,　and　solved　by　Newton＇s　method.　After　that,　pitch　deviations　are　evaluated　according　to　ISO1328-1:2013.　Experiments　are　carried　out　on　a　gear　measurement　center　under　four　groups　of　different　installation　errors.　The　value　of　the　variation　among　total　cumulative　pitch　deviations　of　the　product　gear　obtained　by　this　method　under　different　installation　conditions　is　0.39　mu　m,　whereas　the　variation　obtained　by　the　gear　measurement　center　is　28.66　mu　m.　The　method　can　be　used　to　evaluate　pitch　deviations　in　the　pitch　measurement　under　certain　installation　errors