Abstract: Taking the implementation practice of ultra-low emissions in power plants of Jiangsu Province as the research object, a coupled model system consisting of mesoscale meteorological model MM5 and environmental air quality model CALPUFF was established to study the contribution of the ultra-low emission implementation in thermal power industry to the reduction of ambient air PM_2.5. The impacts as well as how much ambient air PM_2.5 mass concentration is reduced in the province were simulated and calculated respectively in 2013 and 2017, which correspond to the years before and after the ultra-low emission implementation. The results show that the average annual PM_2.5 concentration contributed by the province's thermal power plants at 13 prefecture-level cities was reduced from 8.0 μg/m³ in 2013 to 4.6 μg/m³ in 2017 with the average decrease rate of 42.5%. The environmental air quality monitoring results show that the average annual concentration of PM_2.5 in 13 prefecture-level cities in Jiangsu Province in 2017 was 24.1 μg/m³ lower than that in 2013 with a decrease rate of 32.9%, which is significantly lower than the average annual concentration reduction of PM2.5 contributed by thermal power industry. The difference of 9.6% shows that the emission reduction of pollutants in the thermal power industry has entirely exceeded the emission reduction of pollution sources generated in other industries in Jiangsu Province in the past five years. At last, the route of pollutants control is proposed for the future.