In　order　to　research　the　effects　of　the　dimension　of　the　escape　on　the　strength　and　the　stress　distribution　of　the　shafts,　finite　element　software　ANSYS　was　used　to　research　the　stress　concentration　caused　by　escape　on　shafts　with　different　external　diameters　under　φ30　mm.　The　studies　showed　that　the　stress　concentration　factor　caused　by　escape　specified　by　the　GB　standard,　increased　with　the　increase　of　the　threads　external　diameter.　To　ensure　the　service　life　of　the　shafts,　the　external　diameter　of　the　thread　should　be　increased　about　1.7　times　if　escapes　existed.　The　diameters　of　the　shafts　can　be　accurately　designed　by　finite　element　numerical　analysis　technology,　which　can　not　only　ensure　the　parts　service　life　but　also　reduce　their　quality　and　save　materials.