Piezoelectric sensor, the core device of pulsed electro-acoustic method (PEA), is limited by the properties of piezoelectric materials, so it is difficult to detect three-dimensional charge distribution at high temperature. Laser Doppler vibration measurement technology overcomes the shortcomings of PEA method, and can replace piezoelectric sensors to achieve high-precision detection of acoustic signals. In this paper, according to the performance parameters of laser Doppler vibrometer(LDV), a space charge signal characterization simulation model based on laser Doppler vibration measurement is established to study the influence of Gaussian pulse half peak width on the characterization signal. The results show that when the half peak width is 500ns, the frequency band of the vibration signal is within 3MHz, and the amplitude is 230pm. After filtering and quantization, the vibration signal can well characterize the charge distribution and the spatial resolution of 1mm can be achieved; When the half peak width is 10ns, the bandwidth of the vibration signal is within 200MHz, and the amplitude is 232.6pm. After filtering, the amplitude is attenuated to 13.75pm, which is lower than the displacement resolution of LDV, and the output signal is zero. The analysis shows that the half peak width should not be less than 500ns to ensure that the characteristic signal waveform can characterize the charge distribution without sacrificing spatial resolution.