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<p>Air pollution is a serious environmental issue and leading contributor to disease burden in China. Rapid reductions in fine particulate matter (PM<span class="inline-formula">_2.5</span>) concentrations and increased ozone concentrations occurred across China during 2015 to 2017. We used measurements of particulate matter with a diameter <span class="inline-formula">&lt;2.5</span>&thinsp;<span class="inline-formula">µ</span>m (PM<span class="inline-formula">_2.5</span>) and ozone (<span class="inline-formula">O₃</span>) from more than 1000 stations across China along with Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) regional air quality simulations, to explore the drivers and impacts of observed trends. The measured nationwide median PM<span class="inline-formula">_2.5</span> trend of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">3.4</mn><mspace linebreak="nobreak" width="0.125em"/><mrow class="unit"><mi mathvariant="normal">µ</mi><mi mathvariant="normal">g</mi><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">m</mi><mrow><mo>-</mo><mn mathvariant="normal">3</mn></mrow></msup><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">yr</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="80pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="360c33cd5bbe0cd7a21c3548e76af98d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-11683-2020-ie00001.svg" width="80pt" height="15pt" src="acp-20-11683-2020-ie00001.png"/></svg:svg></span></span> was well simulated by the model (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">3.5</mn><mspace width="0.125em" linebreak="nobreak"/><mrow class="unit"><mi mathvariant="normal">µ</mi><mi mathvariant="normal">g</mi><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">m</mi><mrow><mo>-</mo><mn mathvariant="normal">3</mn></mrow></msup><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">yr</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="80pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="21a0dd38263feecb02dcba92286c635f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-11683-2020-ie00002.svg" width="80pt" height="15pt" src="acp-20-11683-2020-ie00002.png"/></svg:svg></span></span>). With anthropogenic emissions fixed at 2015 levels, the simulated trend was much weaker (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">0.6</mn><mspace linebreak="nobreak" width="0.125em"/><mrow class="unit"><mi mathvariant="normal">µ</mi><mi mathvariant="normal">g</mi><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">m</mi><mrow><mo>-</mo><mn mathvariant="normal">3</mn></mrow></msup><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">yr</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="80pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="b3e4efb61a626e3442634fd15e0b3444"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-11683-2020-ie00003.svg" width="80pt" height="15pt" src="acp-20-11683-2020-ie00003.png"/></svg:svg></span></span>), demonstrating that interannual variability in meteorology played a minor role in the observed PM<span class="inline-formula">_2.5</span> trend. The model simulated increased ozone concentrations in line with the measurements but underestimated the magnitude of the observed absolute trend by a factor of 2. We combined simulated trends in PM<span class="inline-formula">_2.5</span> concentrations with an exposure–response function to estimate that reductions in PM<span class="inline-formula">_2.5</span> concentrations over this period have reduced PM<span class="inline-formula">_2.5</span>-attributable premature mortality across China by 150&thinsp;000 deaths&thinsp;yr<span class="inline-formula">⁻¹</span>.</p>