As　the　wiring　space　on　the　printed　circuit　board　becomes　more　and　more　tight,　especially　in　the　high-speed　backplane　design,　it　is　impossible　for　all　high-speed　signal　lines　to　be　laid　on　the　top　and　bottom　layers　on　the　traditional　coplanar　waveguides.　In　order　to　research　the　transmission　line　performance　of　the　inner　layer　of　the　backplane　and　improve　the　bandwidth　of　the　transmission　line,　this　paper　designs　a　CPW2G　transmission　line　model,　and　research　the　influence　of　its　inner　reference　plane　and　the　return　ground　via　on　the　transmission　bandwidth.Through　modeling　and　simulation,　the-1dB　bandwidth　of　the　CPW2G　transmission　line　can　reach　60GHz　under　the　same　parameter　conditions,　which　is　70.8%　higher　than　the-1dB　bandwidth　of　the　CPWG　transmission　line.　©　2021　IEEE.