Abstract: Considering the structural peculiarity of phase modulator, a novel structural design of optical waveguide phase modulator is proposed in this study, which is different from the traditional structural design. Under the condition of phase velocity matching, with a narrow-width center electrode and a small gap between electrodes, a pint-sized phase modulator has been developed, which has the features of wide broadband and low half-wave voltage (V_π). The 3 dB bandwidth and the V_π of the phase modulator are measured respectively as 17 GHz and 2.8 V at a wavelength of 1 550 nm and the electrode length of 30 mm.