The　kinematic　parameters　of　the　two-wheeled　robot　has　a　great　influence　on　the　robot　localization　and　path　planning.　Since　there　exist　robot　systematic　errors　caused　by　unequal　wheel　diameter　and　uncertainty　about　the　effective　wheelbase,　it　is　difficult　to　acquire　the　exact　kinematic　parameters.　In　order　to　reduce　the　errors,　researchers　introduced　the　UMBmark　to　make　calibration　of　robot　kinematic　parameters.　However,　the　previous　studies　assume　that　the　two　factors　influence　the　robot　localization　independently,　which　is　not　the　case　in　fact.　This　paper　put　forward　an　improved　kinematic　parameters　calibration　method　based　on　the　UMBmark.　Let　the　robot　walk　along　a　straight　path　and　an　equilateral　triangle　path　respectively　and　we　can　calibrate　kinematic　parameters　by　measuring　the　actual　position　errors.　Then　the　optimal　length　of　the　straight　path　was　given　out,　and　it　is　proved　that　the　equilateral　triangle　path　has　better　adaptability　than　the　square　path　has.　Physical　experiment　has　been　carried　out,　and　the　result　verified　the　effectiveness　of　the　proposed　method.　©　2012　IEEE.