The SnO2-based varistor is a kind of new varistor ceramic material with high nonlinear electrical properties and high thermal conductivity. To improve the comprehensive performance, we focus on how to lower the residual voltage ratio of SnO2-based varistor. In this article, the influence of Cr2O3 on the microstructure, nonlinear J-E characteristics and surge current performances have been investigated. By changing mean grain size and bringing oxygen vacancies, different Cr2O3 concentrations make the residual voltage ratio increase or decrease accordingly. The lowest residual voltage ratio we obtained is 1.68, when the content of Cr2O3 is 0.03 mol%, which is comparative to commercial ZnO-based varistor of the same specifications and close to practical use.