Abstract: SnO₂ varistors were sintered in air atmosphere and oxygen-enriched atmosphere (oxygen volume fractions of 30%, 40%, and 50%, respectively), and the effects of oxygen content in sintering atmosphere on microstructure and electrical properties of SnO₂ varistors were studied. The results show that the phase composition and grain size of the varistor sintered in the oxygen-riched atmosphere were similar to those sintered in the air atmosphere, and the varistor had fewer pores and better compactness. With increasing oxygen content in the oxygen-riched atmosphere, the electrical performance of the varistor increased, especially when the oxygen volume fraction was 50%, the nonlinear coefficient of the varistor increased by 46.9%, the voltage gradient increased by 45.9%, and leakage current was reduced by 30.0%.