For　reverse　calculation　of　the　parameters　of　an　involute-center　and　radius　of　basic　circle,　without　knowing　the　center　point　of　basic　circle　of　the　involute,　this　paper　proposes　a　method　as　utilizing　principles　of　Three-Point-Circle　to　calculate　the　initial　values　of　objective　parameters　first　and　optimizing　it　by　solving　the　non-linear　least　squares　with　Gauss-Newton　method　(GN　method),　and　draws　conclusion　that　this　method　can　be　applied　to　calculate　the　parameters　of　an　involute　and　multi　involutes,　and　also　receives　good　effect　when　it　is　utilized　to　determine　the　initial　coordinate　value　of　probe　in　Gear　Measuring　Center.