The Chinese government implemented a series of policies to improve air quality during the Thirteenth Five-Year Plan (13^th FYP). However, the long-term health effects of the 13^th FYP air pollution control policies have not been evaluated, and the outbreak of coronavirus disease 2019 (COVID-19) has brought great uncertainty regarding the evaluation of the effects. In this study, we selected 329 cities in mainland China to study the chronic health effects due to the decrease in fine particulate matter (PM_2.5) during the 13^th FYP. The relative risk (RR) of PM_2.5 exposure was obtained from a previous study, and the total premature deaths were calculated. We also applied the grey prediction model to predict the PM_2.5 concentration in each city in 2020 to evaluate the impacts of COVID-19. The results showed that the annual PM_2.5 concentration was reduced from 49.7 μg/m³ in 2015 to 33.2 μg/m³ in 2020, and premature deaths were reduced from 1,186,201 (95% CI: 910,339–1,451,102) and 446,415 (in key regions, 95% CI: 343,426–544,813) in 2015 to 997,955 (95% CI: 762,167–1,226,652) and 368,786 (in key regions, 95% CI: 282,114–452,567) in 2020, respectively. A total of 188,246 (95% CI: 148,172–224,450) people avoided premature deaths due to the reduction in PM_2.5 concentrations from 2015 to 2020. Although the impacts of COVID-19 in 2020 brought a significant reduction of 35.3% in February (14.2 μg/m³, p < 0.0001) and in March by 17.6% (5.8 μg/m³, p = 0.001), we found that COVID-19 showed few obvious influences on China's long-term air pollution control plans. The observed data and predicted data are very close in annual mean values and showed no statistical significance both in all cities (p = 0.98) and in key regions (p = 0.56) in 2020.