We quantify the impacts of sulfate and nitrate aerosol formation on surface-layer O3 concentrations over China using the one-way nested-grid capability of the global three-dimensional Goddard Earth Observing System chemical transport model (GEOS-Chem). Chemical reactions associated with sulfate formation are simulated to generally increase O3 concentrations in China. Over the North China Plain (NCP) and the Sichuan Basin (SCB), where simulated sulfate concentrations are the largest, ozone concentrations show maximum increases in spring by 1.8 ppbv (3.2%) in the NCP and by 2.6 ppbv (3.7%) in the SCB. On the contrary, nitrate formation is simulated to reduce O3 concentrations by up to 1.0 ppbv in eastern China, with the largest reductions of 1.0 ppbv (1.4%) in summer over the NCP. Accounting for the formation of both sulfate and nitrate, the surface-layer O3 concentrations over a large fraction of eastern China are simulated to increase in winter, spring, and autumn, dominated by the impact of sulfate formation, but to decrease in summer because of the dominant contribution from nitrate formation.