The surface of polyetrafluorethylene (PTFE) membrane is smooth and anti-chemistry. PTFE membrane is bonded to the surface of conventional filter medium and eliminates the need for a primary dustcake. Filtration takes place on the membrane surface and realizes surface filtration. Because the PTFE membrane has the advantage of smooth, chemical stability, long service life and waterproof, it results in excellent dustcake release, high filtration efficiencies and longer service life.