The invention discloses an integrated treatment method capable of desulfurizing, denitrating and dust-removing at the same time, and provides a device which adopts the treatment method. Smoke formed after the combustion in a boiler contains the main ingredients of SO2, NOX and dust, and passes through a plasma generation electrode; generated plasmas contain a large amount of high-energy electronics and act on O2 and H2O to generate a large quantity of active particles, such as H, O, OH and O3. The SO2 and the NOX can perform chemical reaction to generate high-valence state sulfur oxides and nitrogen oxides under the effect of the active particles, and then the sulfur oxides and the nitrogen oxides are combined with introduced ammonia gas to generate ammonium salts; the ammonium salts are recovered and serve as secondary products; and therefore, the desulfurizing and the denitrating are realized. In the process, charged particles in the plasmas can electrify dust particles, so that the charged particles can move directionally under the effect of an additional direct-current bias electric field; and therefore, the function of removing the dust is realized. According to the method and the device, the static electricity dust removal and the plasma desulfurizing and denitrating are integrated, so that the number of power supplies is reduced, the efficiency of a discharge power supply is improved, the energy consumption can be reduced, the investment is saved, the occupied area is reduced, and the cost is reduced.