In this study, an evaluation index of atmospheric oxidation capacity (AOIe) was established. A typical pollution event from October 3 to 8, 2015, and the WRF-Chem air quality model were used to simulate the distribution characteristics of atmospheric oxidation capacity (AOC) in Beijing and the influence of reducing emissions (NOx and VOCs) on regional AOC. The results showed that urban areas have stronger (approximately 11% higher on average) AOC than suburban areas. AOIe_G (the process of valence change in gaseous oxidants) contributed more to the regional AOC during the clean period. AOIe_G also contributed more in the daytime whereas AOIe_P (the process of valence change in particulate state) contributed more at nighttime, with the highest contribution accounting for 72% and 69%, and the corresponding peak concentrations appearing at 14:00 and 06:00, respectively. In addition, compared with NOx reduction, the effect of reducing VOCs on reducing AOC was more significant.