The　broadband　grounded　coplanar　waveguide　(GCPW)　is　the　core　component　for　calibrating　oscilloscope　broadband　probes.　To　accurately　measure　the　bandwidth　of　the　oscilloscope　probe,　obtaining　the　transmission　characteristics　of　the　broadband　GCPW　becomes　the　key　to　achieving　high-precision　calibration.　A　GCPW　time-domain　twice　measurement　system　is　constructed　based　on　femtosecond　laser　excitation　picosecond　electric　pulse　technology　in　the　measuring　principle　of　time-domain　automatic　network　analyzer　(TDANA).　This　involves　taking　two　measurements　in　the　system　to　solve　the　impulse　response　of　the　broadband　GCPW　(twice　measurement　method),　thereby　the　frequency　domain　bandwidth　can　be　obtained.　The　GCPW　is　designed　with　a　post-wall　structure　(vias　placed　along　the　signal　trace),　and　the　processed　sample　is　measured　by　the　twice　measurement　method.　In　this　way,　the　3　dB　bandwidth　of　our　sample　reaches　54.　2　GHz,　which　greatly　agrees　with　the　simulation　result.　The　calibrated　broadband　GCPW　can　be　used　as　a　standard　device　for　calibrating　broadband　probes,　and　its　measured　results　can　be　effectively　traced　to　the　national　benchmark　for　pulse　waveform　parameters.　©　2023　Chinese　Society　for　Measurement.　All　rights　reserved.