Abstract: After the denitrification device using NH_3 and urea as reducing agents is installed in a coal-fired power plant,ammonium bisulfate( ABS) is formed by the reaction of reducing agent NH_3 with sulfur oxides and water vapor in the flue gas. ABS deposition will lead to the reduction of selective catalytic reduction( SCR) and the blockage of downstream thermal equipment,such as air preheater( APH) and electrostatic precipitator( ESP). The formation and deposition of ABS are related to the operating environment,but there are some unclear understandings about the characteristics of ABS in the industry. Therefore,starting from the emergence of the ABS problem,and then the reason why the wide-load denitrification of thermal power plants causes the aggravation of the ABS influence was pointed out,and the behavior of ABS formation,migration and deposition in the SCR reactor and air preheater was reviewed subsequently. The significant characteristics of ABS,such as formation method,formation temperature,dew point temperature,volatilization and deposition characteristics and decomposition characteristics were summarized. Based on the above summary,suggestions for the study of the characteristics of ABS formation-migration-volatility-decomposition-deposition were put forward,and the direction and development trend of studying the overall influence of ABS migration and volatilization characteristics on SCR and air preheaterwas pointed out.