The electrical and dielectric properties of $ZnO-Pr_6O_{11}-CoO-Cr_2O_3-based$ varistors were investigated in the sintering time range of $1~3$ h. Increasing sintering time improved the densification of ceramics, whereas deteriorated the nonlinearity, in which the nonlinear exponent greatly decreased from 55.3 to 38.2 and the leakage current increased from 0.1 to $1.1;{mu}A$. The donor concentration and density of interface states increased in the range of $(1.06~1.60) imes10^8/cm^3;and;(3.15~3.67) imes10^{12}/cm^2$ with increasing sintering time, respectively. while, in dielectric properties, the increase of sintering time increased in the range of $0.0228~0.0505$ in tans and $1.32~1.36;{mu}s$ in relaxation time.