Abstract: Air pollution can exert significant impacts on human health, transportation, agriculture, and etc., thereby causing huge losses in the economy. For many years, air pollution has been severe in Beijing, and coal heating is a major contributor. During 2016–2017, a clean heating-supply transformation was performed to improve the air quality in Beijing. This study compares the different concentrations of particulate matter (PM), PM2.5, PM10, O₃, SO₂, NO₂, and CO, in 2018 to those in 2015 at five stations located in different districts of Beijing to evaluate the role of clean energy heating transformation in improving the air quality. Results show that the concentrations of PM2.5, PM10, SO₂, NO₂, and CO in 2018 all reduced compared with those in 2015, and the averaged reduction is 37.3%, with SO₂ concentration decreasing the most, that is, by 59.2%. Further analysis reveals that the difference in pollutant concentrations between 2018 and 2015 mainly occurs in winter when people use a heating supply. Compared with 2015, the number of heavily polluted days (PM2.5concentration> 150 μg/m³) declined in winter by 91.3% on average and more than 41.3% in other seasons. The averaged difference between the winters of 2018 and 2015 in PM2.5, PM10, SO₂, NO₂, and CO concentrations is 4.8 times that of other seasons with 2.3 times the reduction percentage. Analysis from hourly data demonstrates that a relatively larger decrease mainly occurred at times when much more heating is used. Combined with meteorological conditions, these results imply that the clean energy heating transformation largely improves the air quality, providing a reference for other cities with a similar heating supply.