The invention provides an air purifier. The air purifier is characterized by comprising a draught fan, a silica gel solution filter layer communicated with an outlet of the draught fan, a silica gel filter layer communicated with the silica gel solution filter layer and an air outlet communicated with the silica gel filter layer, wherein the silica gel solution in the silica gel solution filter layer contains a plurality of spherical silica gel bodies and a water solution, the diameters of the spherical silica gel bodies range from 3.5 mm to 4.5 mm, the spherical silica gel bodies are soaked in the water solution, the water solution contains benzoic acid or sodium benzoate, the concentration of the benzoic acid or sodium benzoate ranges from 0.8 % to 1.5%, the silica gel filter layer is composed of a plurality of spherical silica gel bodies, and the diameter of each spherical silica gel body ranges from 3.5 mm to 4.5 mm. Compared with the prior art, the air purifier has the advantages of being capable of effectively filtering small particles and bacteria out of air, high in filtering efficiency, simple in structure and low in manufacturing cost.