The invention discloses a flue gas purifier, which comprises a decontamination chamber, an air inlet pipe and an air outlet pipe which are connected to the decontamination chamber, the air inlet pipe and the air outlet pipe are arranged on the upper part of the decontamination chamber, a flue gas diffusion chamber communicated with the air inlet pipe is provided at the top of the decontamination chamber, a filter cylinder which is perpendicular to a horizontal plane is provided at the sidewall of the decontamination chamber, the opening of the filter cylinder is downwards, the cylinder bottom of the filter cylinder is positioned at the upper part of the decontamination chamber and is communicated with the air outlet pipe, a filter core is provided in the filter cylinder, a filler is provided in the decontamination chamber, and an water outlet is provided at the bottom of the decontamination chamber. The flue gas purifier can effectively solve the problems that the combustion efficiency is low, the environmental pollution is severe and the health of the users is influenced which are existed in a garbage fuel utilization apparatus in the prior art, can provide a flue gas fuel with little pollution and high calorific value, the organic wastes like leaf, wood chip, crops straw, seed shell and the like can be fully utilized, thereby the waste can be deposed and the energy can be saved, so that the flue gas purifier possesses great social benefit.