Abstract: Non-contact electric field sensing technology serves as a solution for voltage measurement at critical nodes in the current power system. This paper aims to achieve high spatial resolution and miniaturization in three-dimensional (3D) pulsed electric field measurement. A novel miniaturized 3D impulse electric field measurement technique based on electro-optic modulation is proposed. A 3D electric field measurement probe utilizing asymmetric straight waveguides has developed. Simulation studies and experimental validation have been conducted to investigate the measurement range, electric field sensing directionality, and temporal waveform reproducibility of the probe. The volume of this 3D probe is approximately 3 cm×3 cm×10 cm, which is approximately ten times smaller than conventional 3D probes, thereby further enhancing the spatial resolution of electric field measurement. From the evaluation of sensor measurement performance on lightning impulse test platform, the results indicate that the probe not only accurately reflects the temporal waveform of the measured lightning impulse electric field but also exhibits good directional characteristics. Within the rated range of 20% to 120%, the comprehensive measurement error of the sensor is better than 3%, enabling accurate measurement of lightning impulse voltage.