(Ca, Ta)‐doped TiO2 varistors with high nonlinear coefficients were obtained by ceramic sintering process. The nonlinear electrical and dielectric properties of the samples doped with 1.0 mol% Ca and different concentrations of Ta (0.05–2.0 mol%) were investigated. Especially, the effects of Ta dopant on the nonlinear and dielectric properties of the (Ca, Ta)‐doped TiO2 varistors were studied in detail. When the concentration of Ta is 0.5 mol%, the sample possesses the highest nonlinear coefficient (16.6). By analogy to a grain‐boundary atomic defect model, the effects of Ta and the nonlinear electrical behavior of the TiO2 system were explained.