Despite the rapid development of China’s industries, the small-scaled boilers (SCBs) still occupy a large proportion. The huge pollutant emissions of SCBs should be paid more attention due to the lack of pollutant removal devices (RDs). In this study, various SCBs (the involved fuels include coal, gangue, coke oven gas, coal gas, and natural gas) applied in bathing, heating, power generation, and coke and cement making were investigated for SO2, NOx, and PM emission factors (EFs). EFs were expressed by pollutant mass per fuel consumption as EFI, per product yield as EFII, per industrial output as EFIII, and per power generation as EFIV. Among 17 civil SCBs, 4, 14, and 10 ones were not equipped with PM, NOx, and SO2 RDs, respectively. Generally the EFI values for 17 civil SCBs decreased with the increase of their coal consumptions. The average of NOx EFI values for 3 SCBs with NOx RDs installed was 2.00 kg t-1, while it was 3.16 kg t-1 for 17 SCBs. The sulfur content of coal and SO2 removal rate were important influencing factors on the SO2 EFI values. The 4 companies without PM RDs possessed the average of EFI values as 23.9kg t-1, higher than the corresponding 5.41 kg t-1 for 13 ones equipped with PM RDs. EFI, EFII, and EFIV for 9 coal-fired power plants (PPs) showed the same trends, the EF values for coal-fired PPs decreased from 6MW to 330 or 300 MW, while the 600 MW possessed slightly higher EFs than 330 MW. Gas-fired PPs possessed higher NOx EFs than coal- and gangue-fired ones. Gangue-fired PPs possessed significantly higher EFs than coal-fired PPs with the same individual block power capacity. Because the flue gas for coking industry was not fully emitted from combustion process, there was no correlation between the EFs (expressed as EFII and EFIII) and their coke productions or industrial outputs. The NOx EFs for coking were higher than SO2 and PM due to the lack of NOx RDs. For 6 small- and medium-sized cement companies, higher PM EFI occurred at the company with lower cement production. A reverse trend possessed by NOx EFI, high combustion temperature of company with high cement production was the possible explanation.