<p>High-voltage electric pulse (HVEP) technology is a new type of rock-breaking technique with high efficiency and eco-protective characteristics. The strain field evolution, fracture process and fragmentation characteristics of red sandstone specimens under HVEP were investigated. Electrical breakdown experiments were conducted on red sandstone specimens with sizes ranging from 80&#xa0;mm × 80&#xa0;mm × 80&#xa0;mm to 120&#xa0;mm × 120&#xa0;mm × 120&#xa0;mm under the same discharge voltage. The strain field evolution (SFE) and crack propagation behavior of the specimen were monitored by digital image correlation (DIC) technology. In addition, the fracture characteristics of the crack network on the monitoring surface were extracted by image recognition technology. The surface crushing energy <i>E</i>_<i>FA</i> of the specimens was calculated using the theoretical formula. The experimental results show that the shape of the surface strain concentration zone (SCZ) changes significantly with the increase in the specimen size. The corresponding surface fracture mode transitions from the intersection of multiple cracks to the line parallel to the plasma channel. However, the principal strain perpendicular to the axis of the plasma channel is dominant in the fracture process of specimens with different sizes. Consequently, transverse cracks penetrate these specimens more rapidly. The fractal dimension (<i>D</i>_<i>f</i>) of the surface crack network is negatively correlated with the specimen size. Meanwhile, the calculation results indicate that the <i>E</i>_<i>FA</i> of the rock specimen decreases with increasing specimen size. Subsequently, we established a three-dimensional finite element model and validated it against the experimental results. Based on this model, we analyzed the propagation and attenuation of stress waves in specimens of different sizes subjected to HVEP. Furthermore, we elucidated the damage evolution within the specimens and clarified the fracture mechanism of red sandstone under HVEP.</p>