Abstract In this article, CaCu₃Ti₄O₁₂ (CCTO) and Zr-doped CaCu₃Ti_3.95Zr_0.05O₁₂ (CCTZO) particles were fabricated by the sol–gel combustion method, and then, CCTO/LDPE and CCTZO/LDPE composite films were prepared by the melt-blending and hot briquetting. The microstructures and dielectric properties of fillers and LDPE composites were investigated in detail. Results showed the lattice expansion of CCTZO caused by Zr doping reduced grain size, increased size uniformity, and remarkably reduced dielectric loss and conductivity. Compared with CCTO, small-size CCTZO enhanced dielectric constant of LDPE by 88.5% (∼3.45) due to enhanced interfacial polarization included by ultrahigh interfacial area (∼3.0 × 10⁵ m²), remaining a lower loss tangent (0.013) and conductivity (2.42 × 10⁻¹³ S·cm⁻¹) for the 10 vol% CCTZO/LDPE composite. Furthermore, finite element simulation proofed small-size and uniform CCTZO particles played a prominent role in homogenize electric field distribution in LDPE composite, which was beneficial for the use of these composites in the high voltage power cable field.