ZnO-SrCO3-Co2O3-SiO2 varistor ceramics were fabricated using the solid state method. Structural, morphological characterizations and varistor characteristics of samples were systematically studied. Average grain size is gradually reduced from 13.74 to 6.67 μm, resulting in a simultaneous increase of breakdown gradient E1 mA from 157.14 to 339.29 V mm−1. An increase of doping amount of SiO2 from 0 to 0.50 mol% contributes to the positive influences on double Schottky barrier of ZnO-SrCO3-Co2O3 varistors. The sample doped by 0.50 mol% SiO2 exhibits the highest height of double Schottky barrier φB of 2.99 eV resulting in the high nonlinear coefficient α equal to 76.83 and small value of leakage current density IL less than 0.29 μA cm−2 among the samples, which may be attributed to the solid solution reactions of SiO2 and Co2O3 in grain boundaries. The fabrication of ZnO-SrCO3-Co2O3-SiO2 represents the low-cost, sustainable development and environmental friendliness, providing a high performance candidate material for dominant ZnO-Bi2O3 based varistor ceramics.