In this Letter, we reported the preliminary results of an integrating periodically capacitive-loaded traveling wave electrode (CL-TWE) Mach–Zehnder modulator (MZM) based on InP-based multiple quantum well (MQW) optical waveguides. The device configuration mainly includes an optical Mach–Zehnder interferometer, a direct current electrode, two phase electrodes, and a CL-TWE consisting of a U electrode and an I electrode. The modulator was fabricated on a 3 in. InP epitaxial wafer by standard photolithography, inductively coupled plasma dry etching, wet etching, electroplating, etc. Measurement results show that the MZM exhibits a 3 dB electro-optic bandwidth of about 31 GHz, a Vπ of 3 V, and an extinction ratio of about 20 dB.