The microstructure and electrical properties of ZnO-Bi2O3 system with Bi2O3(0.5~5mol%) content have been investigated in relatin to sintering temperature and atmosphere. The grain size of ZnO increases sharply with Bi2O3(0.5~5mol%) content, but over 0.5mol% Bi2O3 increased less rapidly when sintered at 120$0^{circ}C$. Electrical characteristics varied with sintering atmosphere and air-sintered conditions showed comparatively lower nonlinear exponents than the double-crucible conditions. Calculated barrier voltage was about 1.7V.