Abstract: Since the Action Plan of Air Pollution Prevention and Control, the PM_2.5 concentrations in key regions has decreased rapidly while O₃ concentration has gradually increased. The demand of coordinated control of PM_2.5 and O₃ is urgent for the Chinese government. Understanding the responses of PM_2.5 and O₃ to changes in precursor emissions and meteorological conditions is of great significance for formulating coordinated control strategies of PM_2.5 and O₃. By using the air quality model and response surface model, this study evaluated the response of 2.5 and 3 concentrations to the changes of precursors and meteorological conditions. Based on the analytical response relationship, policy recommendations on precursor emission reduction, regional division of joint prevention and control, and target setting were proposed. Results show that: (1) VOCs emission reduction is beneficial to reduce both PM_2.5 and O₃ concentration in all provinces. Insufficient NO_x emission reduction will increase O₃ concentration in most key areas and PM_2.5 concentration in Beijing-Tianjin-Hebei region, and the VOCs/NOx emission reduction ratio is 45% and 20% on average to avoid this adverse effect. For the Beijing-Tianjin-Hebei region, the joint control of Henan and Shandong may need to be considered. For the Yangtze River Delta and Pearl River Delta, the joint control of Jiangxi and Fujian may be more important in the future. (3) Meteorological conditions have a great influence on PM_2.5 and O₃ background values. The effects of three-year moving average and five-year moving average on reducing PM_2.5 fluctuation in each region are 35-81% and 60-86%, and the effects of reducing O₃ fluctuation are 40-67% and 53-87%. Applying multi-year moving averages to mitigate the variation of meteorological conditions helps to scientifically set and assess the targets for PM_2.5 and O₃.