Beijing, the capital of China, revised the emission standard for air pollutants for boilers in 2015. To promote fulfillment of the new standard, the “coal to gas project” and the “reward replaces subsidy policy for low-NOx retrofits of boilers” were implemented recently, and the emission of pollutants from boilers has significantly changed as a result. In this study, a comprehensive unit-based emission inventory of multiple air pollutants, including PM10, PM2.5, CO, SO2, NOx, VOCs and NH3, from both coal-fired and gas-fired industrial boilers in Beijing in 2015 was established with data on annual activity and category-specific emission factors, and scenario analysis and the CMAQ model were used to forecast the environmental impacts of the revised standard during the heating season in Beijing. Our results showed that in 2015, the emissions of CO, NOx, PM2.5, PM10, SO2, NH3 and VOCs from the industrial boilers in Beijing were about 51,745 t, 27,943 t, 10,143 t, 14,624 t, 20,227 t, 197.55 t and 1304 t, respectively. Coal-fired boilers were the major source of CO, SO2, PM2.5 and PM10, while gas-fired boilers were the major source of VOCs and NH3. Furthermore, in IPC-1 and IPC-2 scenarios, which represent the different levels of implementation of the “low-NOx retrofits policy” as well as the replacement of all coal-fired boilers with gas-fired boilers, the ambient concentration of PM2.5 and SO2 was reduced by about 7.1% and 9.5%, respectively, and the concentration of NO2 was reduced by about 4.4% in IPC-1 and 3.7% in IPC-2 during the heating season in Beijing.