Abstract: At present, serious air pollution caused by the PM_2.5 occurs in China. The coal-fired power plants（CFPPs） are one of the major sources of the PM_2.5 in the atmosphere. Although the selective catalytic reduction（SCR） DeNO_x devices are installed in CFPPs on a large scale for reducing NOx and secondary PM_2.5 produced by NOx, primary PM_2.5, mainly are fine particles of ammonium（bi）sulfate, increases through the SCR DeNO_x devices. Consequently, the physical and chemical characteristics of PM_2.5 are changed by the SCR DeNO_x process, which was clarified along with the influence of SCR DeNO_x process for emission of fine particles in CFPPs. The generation and conversion of fine particles of ammonium（bi）sulfate were focused on together with the influence factor. Finally, the paper made prospects of future study direction of generation and control of fine particles in SCR DeNO_x process.