The microstructure, electrical properties, and clamping voltage characteristics of $ZnO-Pr_6O_{11}-CoO-Cr_2O_3-Y_2O_3(ZPCCY)-based$ varistor ceramics sintered at $1350^{circ}C$ were investigated as a function of sintering time from 1 to 3 h. With increasing sintering time, the average grain size and density increased in the range of $11.4~16.0;{mu}m$ and $5.34~5.54g/cm^3$, respectively, in accordance of increasing sintering time. The nonlinear exponent decreased in the range of $60~26$ and the leakage current increased in the range of $1.3~10.7;{mu}A$ with increasing sintering time. The clamping voltage ratio increased in the range $1.58~1.65$ for ratio surge current of 10 A as the sintering time increased.