In　this　paper,　the　grounded　coplanar　waveguide　(GCPW)　used　for　the　calibration　of　high-bandwidth　digital　real-time　oscilloscope　probes　is　studied.　First,　according　to　the　characteristic　impedance　formula　of　the　grounded　coplanar　waveguide　without　via　holes,　the　sizes　of　GCPW　are　adjusted　so　that　the　characteristic　impedance　is　50Ω.　Moreover,　the　influence　of　via　holes　on　the　bandwidth　of　the　GCPW　is　studied　through　simulation　software,　at　the　same　time　the　sizes　and　position　of　the　via　holes　are　changed　to　increase　the　GCPW　bandwidth　to　50　GHz.　The　sizes　of　the　GCPW　with　via　holes　is　further　changed　to　eliminate　the　effect　of　via　holes　on　the　characteristic　impedance.　The　GCPW　is　made　by　machining　on　the　basis　of　the　simulation　data,　then　its　S-parameters　are　measured　by　the　vector　network　analyzer.　In　the　frequency　range　of　DC-50GHz,　S21　is　greater　than　-2.2dB　and　S11　is　less　than　-14dB.　The　research　results　show　that　the　bandwidth　and　transmission　characteristics　of　the　GCPW　can　meet　the　requirements　of　calibration.　©　2021　IEEE.