The invention discloses a flue gas purification device capable of efficiently desulfurizing and denitrifyingand an implementation method of the device, and belongs to the technical field of flue gas purification. The flue gas purification device comprises a denitrification tank body, a mixing preliminary reaction device is arranged at the bottom end of the denitrification tank body, a secondary mixing assembly is arranged in the denitrification tank body above the mixing preliminary reaction device, and the top end of the denitration tank body is connected with the catalytic reactor through a flow guide pipeline. According to the flue gas purification device capable of efficiently desulfurizing and denitrifying and the implementation method of the device, the influence on the gas quality is avoided, and due to the inverted conical arrangement, impurities can conveniently fall off under the action of gravity, the cleaning efficiency is improved, the mixing uniformity is ensured, the denitrifying time is saved, denitrifying is effectively performed, the denitrifying effect is effectively ensured, the desulfurizing effect is improved, and the resource waste is reduced; precipitation and solidification are prevented, the reaction quality is guaranteed, the dispersion uniformity is improved, the reaction uniformity is guaranteed, the desulfurization speed is increased, an adsorption fiber layer adsorbs water and impurities, and the quality of filtered gas is guaranteed.