A　grounded　coplanar　waveguide　(GCPW),　as　a　millimeter　wave　special　transmission　line,　can　be　used　to　calibrate　broadband　oscilloscope　probes.　A　method　to　change　the　through-hole　structure　to　widen　the　GCPW　is　investigated　in　this　paper.　The　effect　of　the　through-hole　array　on　the　band-width　of　the　GCPW　is　investigated　and　verified　using　COMSOL　Multiphysics　simulation　software.　Finally,　the　S-parameters　of　the　fabricated　GCPWs　are　measured　by　a　vector　network　analyzer,　and　the　results　show　that　they　have　an　insertion　loss　＞　−3　dB　and　return　loss　＜　−10　dB　in　the　frequency　range　of　DC　to　60　GHz,　which　satisfies　the　design　requirements.　©　2023　by　the　authors.