Abstract: The Mach-Zehnder traveling wave LiNbO3 optical modulator with thicker electrodes and relatively thicker SiO2 buffer layer have been analysed using conformal mapping, taking into account the dependence of the modulation characteristics on the thickness of electrodes and buffer layer at the same device. The relation between the parameters and the modulation characteristics, such as effective index, characteristic impedance, half-wavelength voltage and conductor loss, have been obtained to select the proper thickness of the electrodes and buffer layer to optimize the performance of the modulator. By using the calculation results, the velocity matching and impedance matching are achieved approximately to realize the broadband modulation.