We investigated the sintering and electric properties of ZnO-1.0 at% $TeO_2$ (ZT1) and 1.0 at% Mn-doped ZT1(ZT1M1) system. $TeO_2$ itself melts at $732^{circ}C$ in air but forms the $ZnTeO_3$ or $Zn_2Te_3O_8$ phase with ZnO as increasing temperature and therefore retards the densification of ZnO to $1000^{circ}C$. In ZT1M1 system, also, the densification of ZnO was retarded up to $1000^{circ}C$ and then reached > 90% of theoretical density above $1100^{circ}C$. It was found that a good varistor characteristics(nonlinear coefficient $a{sim}60$) were developed in ZT1M1 system sintered at $1100^{circ}C$ due to Mn which known as improving the nonlinearity of ZnO varistors. The results of C-V characteristics such as barrier height (${Phi}_b$), donor density ($N_D$), depletion layer (W), and interface state density ($N_t$) in ZT1M1 ceramics were $1.8{ imes}10^{17}cm^{-3}$, 1.6 V, 93 nm, and $1.7{ imes}10^{12}cm^{-2}$, respectively. Also we measured the resistance and capacitance of grain boundaries with temperature using impedance and electric modulus spectroscopy. It will be discussed about the stability and homogeneity of grain boundaries using distribution parameter ($alpha$) simulated with the Z(T)"-logf plots.