The varistor properties of ZnO-Pr$_{6}$O$_{11}$-CoO-based ceramics doped with Sm$_2$O$_3$were investigated in the addition range of 0.0~2.0 mol% Sm$_2$O$_3$at sintering temperature of 130$0^{circ}C$ and 135$0^{circ}C$. As Sm$_2$O$_3$ content is increased, the breakdown voltage was increased in the range of 348.9~521.8 V/mm for ceramics sintered at 130$0^{circ}C$ and 8.5~381.3 V/mm for ceramics sintered at 135$0^{circ}C$. On the whole, the increase of sintering temperature led to the low nonlinearity regardless of Sm$_2$O$_3$content. ZnO-Pr$_{6}$O$_{11}$-CoO-based ceramics doped with 1.0 mol% at each sintering temperature exhibited the most superior varistor properties, with the nonlinear exponent of 42.1 at 130$0^{circ}C$, 36.8 at 135$0^{circ}C$ and the leakage current of 9.2 $mu$A at 130$0^{circ}C$, 11.7 $mu$A at 135$0^{circ}C$.EX>.EX>.