<p>In order to solve the problem of increased leakage current and decreased aging stability of ZnO varistors caused by rare earth doping, this study systematically investigates the multiple functional mechanisms of B₂O₃ in co–doped ZnO systems containing Ga₂O₃, Y₂O₃, and Al₂O₃. By adjusting the content of B₂O₃ (0–0.4&#xa0;mol%), it was found that moderate doping of B₂O₃ (0.3&#xa0;mol%) can significantly improve material properties: the synergistic effect of B₂O₃ and Y₂O₃ promotes the formation and distribution of fine spinel phases, achieves grain size refinement from 6.7&#xa0;μm to 5.85&#xa0;μm, and improves the uniformity of the microstructure of varistors. More importantly, B₂O₃ doping promotes the diffusion and grain boundary segregation of transition metal oxides, increasing the Schottky barrier height from 2.02&#xa0;eV to 2.74&#xa0;eV (0.3&#xa0;mol% doping), significantly improving the electrical performance of ZnO varistors. The electrical performance test shows that the doped 0.3&#xa0;mol% B₂O₃ sample exhibits excellent comprehensive performance: its voltage gradient is 505&#xa0;V/mm, leakage current density is 0.87 μA/cm², nonlinear coefficient is 92, residual voltage ratio is 1.52, and it has excellent aging stability. The decrease in residual voltage ratio and the improvement in aging stability are mainly attributed to the synergistic effect of B₂O₃ inhibiting Zn ion migration and Ga₂O₃/Al₂O₃ increasing grain conductivity; This study elucidates the modification mechanism of B₂O₃ in ZnO varistors, providing important basis for the development of high–performance varistor materials.</p>