China is confronting increasing ozone (O.sub.3) pollution that worsens air quality and public health. Extreme O.sub.3 pollution occurs more frequently under special events and unfavorable meteorological conditions. Here we observed significantly elevated maximum daily 8 h average (MDA8) O.sub.3 (up to 98 ppb) during the Chinese National Day holiday (CNDH) in 2018 throughout China, with a prominent rise by up to 120 % compared to the previous week. The air quality model shows that increased precursor emissions and regional transport are major contributors to the elevation. In the Pearl River Delta region, the regional transport contributed up to 30 ppb O.sub.3 during the CNDH. Simultaneously, aggravated health risk occurs due to high O.sub.3, inducing 33 % additional deaths throughout China. Moreover, in tourist cities such as Sanya, daily mortality even increases significantly from 0.4 to 1.6. This is the first comprehensive study to investigate O.sub.3 pollution during the CNDH at the national level, aiming to arouse more focus on the O.sub.3 holiday impact of the public.