In experiment it has been found that the output waveform of integrated optical waveguide electric field sensor is overlapped by interference signal with frequency of hundreds of kilohertz, which leads to a distortion of the detected electric field signal. The resonance phenomenon is analyzed theoretically based on the piezoelectric effect of LiNbO3 crystal. By comparing the resonant frequency value of theoretical calculation with that of measurement, it shows that the resonance is mainly influenced by the width of LiNbO3 substrate. For lighting impulse detecting, an integrated optical waveguide electric field sensor with 3 mm substrate width is designed and experimental results demonstrate that the resonance phenomenon has been obviously suppressed under -30 dB.