An　ultra-compact　rectangular　Mach-Zehnder　(MZ)　interference　Electro-Optic　(EO)　modulator　on　InGaAsP/InP　platform　was　proposed.　This　modulator　consists　of　novel　trench　couplers　and　90°　waveguide　bends.　T　type　microstrip　Travelling-Wave　(TW)　electrodes　were　designed　for　the　L-shape　waveguide　phase　shift　arm　of　the　MZ　modulator.　First　of　all,　an　upper　bandwidth　limit　of　this　modulator　was　evaluated　by　using　an　equivalent　circuit　model　of　the　TW　electrodes.　According　to　microwave　characteristics　such　as　impedance　match,　return　loss　and　bandwidth,　the　transmission　and　input/output　of　electrodes　and　structure　parameters　of　transition　regions　were　optimized　through　a　finite　element　analysis　method.　The　simulation　results　show　that　being　limited　by　the　input　of　electrodes　and　transition　regions,　the　overall　TW　electrodes　exhibit　an　impedance　match　of　＞42Ω,　return　loss　of　20　GHz　are　obtained　in　terms　of　the　fabricated　Ti/Au　electrodes　on　an　InP　substrate.　©　2017,　Science　Press.　All　right　reserved.