A novel LiNbO₃ modulator based on Si₂N₂O substrate is proposed. Using the finite element method,the proposed modulator has been analyzed. The optimum structure parameters of the novel modulator are obtained. The modulator operates with a 3 dB optical bandwidth of 120 GHz,a half-wave driving voltage of 3.5 V,and characteristic impedance of 50.32Ω. The results show that broad bandwidth and low half-wave voltage can be achieved simultaneously. It is a promising candidate for future ultra-high-speed optical fiber transmission system.