Abstract: Aiming at the serious ash wrapping and hardening of the electrode line of the electrostatic precipitator under the ultra-low emission condition of a 300 MW coal-fired unit in a power plant, the key influencing factors of the formation of ash wrapping on the pole wire of the electrostatic precipitator were studied by analyzing the loss on ignition, soluble ion concentration, ash composition, particle size and specific resistance characteristics of the ash deposited samples, combined with the ultra-low emission operation characteristics of the boiler. The results show that the content of NH■,SO■ and SO_3 in the ash-coated samples on the electrode wire of the low-temperature electrostatic precipitator are all higher, confirming that the main reason for the ash-coated sample of the electrostatic precipitator is the escape of ammonia from the SCR denitrification system and the combination with the ash. SO_3 in the flue gas reacts to generate ammonium hydrogen sulfate. Due to the low operating temperature of the low-low temperature electrostatic precipitator, it is difficult to decompose the ammonium hydrogen sulfate in the flue gas once it has formed, resulting in serious dusting of the electrode wire of the electrostatic precipitator. At the same time, due to the excessive humidity of the flue gas at the inlet of the precipitator, the viscosity of the fly ash increases, which aggravates the phenomenon of ash wrapping and hardening of the electrode wire of the electrostatic precipitator. Ammonium bisulfate changes the properties of fly ash and reduces the particle size of fly ash. At the same time, the adhesion of ammonium bisulfate affects the charging of the electrostatic precipitator, resulting in a decrease in the dust removal efficiency of the electrostatic precipitator and further aggravating the phenomenon of polar line ash deposition. Therefore, in order to reduce the phenomenon of dust wrapping and hardening of the electrostatic precipitator, it is necessary to effectively control the moisture content of the flue gas at the inlet of the electrostatic precipitator, and at the same time strictly control the key influencing factors such as ammonia escape and SO_3 generation concentration in the denitrification system.