Abstract. Meteorological conditions play important roles in the formation of ozone (O3) and fine particulate matter (PM2.5). China has been suffering from serious regional air pollution problems, characterized by high concentrations of surface O3 and PM2.5. In this study, the Community Multiscale Air Quality (CMAQ) model was used to quantify the sensitivity of surface O3 and PM2.5 to key meteorological parameters in different regions of China. Six meteorological parameters were perturbed to create different meteorological conditions, including temperature (T), wind speed (WS), absolute humidity (AH), planetary boundary layer height (PBLH), cloud liquid water content (CLW) and precipitation (PCP). Air quality simulations under the perturbed meteorological conditions were conducted in China in January and July of 2013. The changes in O3 and PM2.5 concentrations due to individual meteorological parameters were then quantified. T has a great influence on the daily maximum 8h average O3 (O3-8h) concentrations, which leads to O3-8h increases by 1.7 in January in Chongqing and 1.1ppbK1 in July in Beijing. WS, AH, and PBLH have a smaller but notable influence on O3-8h with maximum change rates of 0.3ppb%1, 0.15ppb%1, and 0.14ppb%1, respectively. T, WS, AH, and PBLH have important effects on PM2.5 formation of both in January and July. In general, PM2.5 sensitivities are negative to T, WS, and PBLH and positive to AH in most regions of China. The sensitivities in January are much larger than in July. PM2.5 sensitivity to T, WS, PBLH, and AH in January can be up to 5gm3K1, 3gm3%1, 1gm3%1, and +0.6gm3%1, respectively, and in July it can be up to 2gm3K1, 0.4gm3%1, 0.14gm3%1, and +0.3gm3%1, respectively. Other meteorological factors (CLW and PCP) have negligible effects on O3-8h (less than 0.01ppb%1) and PM2.5 (less than 0.01gm3%1). The results suggest that surface O3 and PM2.5 concentrations can change significantly due to changes in meteorological parameters, and it is necessary to consider these effects when developing emission control strategies in different regions of China.