The utility model discloses a high-efficiency electric demisting device for removing PM2.5 superfine dust and SO3 acid mist. The device comprises a wet electrostatic precipitator, an alkali liquor supply device and a water film pH detection device, wherein the alkali liquor supply device comprises a flowmeter and a spraying device; the flowmeter controls the liquid outlet quantity of the spraying device; the spraying device is arranged above the wet electrostatic precipitator; the water film pH detection device comprises a collecting tube and a pH meter; the collecting tube is arranged below the wet electrostatic precipitator; and the pH meter is connected with the flowmeter. The utility model has the advantages that: the superfine dust PM2.5, the SO3 acid mist, heavy metals and other pollutants, which cannot be removed from desulfurized flue gas by the conventional environment-friendly equipment, are removed; by the device, a removal rate of the superfine dust PM2.5 is more than or equal to 95 percent, a removal rate of SO3 aerosol is more than or equal to 93 percent and a removal rate of heavy metal mercury is more than or equal to 80 percent; and a gas-gas heater (GGH) is not required to be arranged to improve the temperature of the flue gas treated by the device, and a chimney is prevented from being corroded.