The invention discloses a porous composite filter tube. The filter tube comprises a tube-shaped structural layer with the thickness of 2-10mm, wherein the surface of the structural layer is provided with a functional layer with the thickness of 50-200mu m, the aperture of the structural layer is 20-150mu m, and the aperture ratio of the structural layer to the functional layer is 2.5-5. The invention also discloses a preparation method of the porous composite filter tube and the method comprises the following steps: weighting composite layer powder and carrier to prepare suspension liquid, adopting fluidization technology to distribute air and stir, then adopting heterogeneous atomization technology to ensure that the suspension liquid to perform atomization deposition or be coated on the outer surface of the matrix of porous material, sintering at 600-1400 DEG C under vacuum or hydrogen atmosphere, and keeping temperature for 1-3 hours to prepare the porous composite filter tube. The invention increases the filtration precision and permeation flux of the filtering element, overcomes the defects of ceramic porous materials and metal porous materials prepared by conventional sintering, has high strength and good filterability and breathability, has corrosion resistance, oxidation resistance and high temperature resistant, and is not easy to break.