Abstract: In recent years, abnormal events involving electrostatic precipitator of coal-fired power plant occur frequently, of which more serious situation is the collapse of ash hopper of electrostatic precipitator, resulting in forced unit outage and great economic loss. Through the analysis of an event occurred in the operation of an electrostatic precipitator of a 2×660 MW power plant, which involves the abnormality of A-train of electric field ash hopper level meter, leading to full of ash hopper and tripping after electric field frequency flicker, and finally hopper deformation, the paper puts forward targeted measures to prevent further deterioration of the event.