Our polypropylene melt-blown cartridge is made of polypropylene superfine fiber but hot melt entangled. The production process does not use any chemical adhesive, and the melt-blown process makes the fibers randomly self-adhesive in space to form a three-dimensional microporous structure, which has a larger specific surface area, higher porosity (≥80%), finer pore size (pore size ≤1μm) and excellent filtration performance far higher than other ordinary filter materials compared with traditional fabrics and combed non-woven materials. As the fiber diameter and accumulation density change controllably in the direction of the diameter of the cartridge, it forms a multi-layer gradient structure from inner dense to outer gradient, which can improve the filtration precision and dirt-holding capacity and constitute a multi-layer gradient structure with low differential pressure, and is a cartridge product with deep filtration performance.