In the last twenty years, the waste-to-energy (WTE) capacity of China has become greater than any other nation. This study examines the environmental performance of the Chinese WTE power plants, including greenhouse gas (GHG), SO2, NOx, HCl, dioxins, particulate matter (PM), and heavy metal (HMs, 11 types) emissions, from 2005 to 2020. The results showed that GHG, NOx, and HCl national emissions increased with increasing WTE capacity. In contrast, PM, CO, SO2, and dioxins peaked in 2015 and gradually declined by 26%, 33%, 28%, and 82%, respectively, in 2020. MSW generation intensity, GDP per capita, and population were factors driving up pollutant emissions, whereas enhancing emission control and MSW treatment structure were key to lower emissions. Between 2005 and 2020, emission factors decreased by 22%-96%. Replacing landfilling by combustion with energy recovery (WTE) reduced the carbon footprint by 137 million tons of CO2-eq in 2020. Limiting emissions of PM, SO2, and NOx in line with the ultra-low emission (ULE) requirements can result in a yearly health benefit of US$18.4 million.