The electrical stability against surge stress of varistors, which are composed of Zn-Pr-Co-Cr-Y oxide system, were investigated at different sintering times. As sintering time increases, the varistor voltage and nonlinear exponent decreased in the range of $279.6~179.1$ and $52.5~24.9$, respectively. On the contrary, the leakage current and dielectric dissipation factor increased in the range of $1.2~9.8;{mu}A$ and 0.0461~0.0651 with increase of sintering time. For all varistors, the variation rates of V-I characteristic parameters against surge stress were more strongly affected in order of varistor voltage ${ ightarrow}nonlnear$ $exponent{ ightarrow}leakage$ current. On the whole, the electrical stability against surge stress increased with increasing sintering time. Conclusively, it is assumed that the varistors sintered for 2 h exhibited comparatively good characteristics, in view of overall characteristics.