ZnO-Bi2O3-MnO2-Cr2O3 varistor ceramics doped with different amounts of silicon dioxide (SiO2) were prepared by a conventional solid-phase sintering method. The phase composition and microstructure of the samples were investigated by X-ray diffraction and scanning electron microscopy. The electrical properties were measured by sourcemetry and inductance capacitance resistance, and the double Schottky barrier parameters were measured by a capacitance-voltage characteristic method. The results show that when the frequency is near 105 Hz, the relative dielectric constant (εr) decreases rapidly since the polarization cannot change with the frequency of electric field, resulting in the corresponding loss peak. The loss peak (tanδ) firstly decreases and then increases with the increase of the doping amount, and its maximum tanδ is obtained witrhout SiO2 and the minimum tanδ is achieved at 1.0% SiO2. The value of tanδ at a frequency of 105 Hz is reduced by doping SiO2. The nonlinear coefficient firstly increases and then decreases with the increase of SiO2 doping amount. The value of α reaches 43.36, the value of φb is 1.98 eV at 10 kHz, the donor concentration is 2.97×1024 m-3, and the leakage current IL is 0.31 μA/cm2 at SiO2 doping amount of 1.0%.