Ethylene-butyl acrylate copolymer (EBA) was used as the matrix resin, combined with highly conductive carbon black (CB) filler to fabricate semi-conductive shielding materials via melt blending. The effects of CB content on the microstructure and key properties were investigated. The results demonstrate a significant decrease in volume resistivity and diminished positive temperature coefficient (PTC) effect with increasing CB loading, indicating improved temperature stability. When the CB content reaches 32 wt%, the material exhibited a room-temperature volume resistivity of 14.7 Ω·cm and a PTC value of 11.5. The tensile strength initially increases but declined beyond a certain CB threshold, whereas elongation at break consistently decreased with higher filler content. Rheological results revealed typical “shear-thinning” behavior, with storage modulus, loss modulus, and complex viscosity gradually increasing at higher CB concentrations. This work elucidates the multifaceted role of CB concentration in determining the performance of shielding material, providing valuable insights for optimizing formulations to advance the development of high-voltage cables.