Abstract: Polyacrylonitrile (PAN) nanofibers were fabricated by electrospinning and collected on sheath-core polyethylene-polypropylene (PE-PP) bicomponent microfiber web to prepare PAN/PE-PP monolayer composite fiber webs. Then several monolayer composite webs were stacked and strengthened by thermal bonding to prepare PAN/PE-PP multilayer composite filters. The effects of the number of layers of PAN/PE-PP composite webs and electrospinning time on the pore size and the filtration performance were studied. The results show that the pore size parameters of multilayer composite materials are similar with that of monolayer composite material, but the pore structures of the two materials are different. At the same total areal density and total electrospinning time, when the number of layers of PAN/PE-PP composite webs is more than 10, the filtration efficiency and quality factor Q_F of PAN/PE-PP multilayer composite filters are significantly larger than that of PAN/PE-PP monolayer composite filter, and the resistance is increased slightly. Compared with PAN/PE-PP monolayer composite filter, the filtration efficiency of 20 layers of PAN/PE-PP composite filter to ≥0.3 μm particles is increased by 33%, the resistance is increased by 5 Pa, and the Q_F is increased by 30%. At the same total areal density and number of layers, when the electrospinning time is prolonged to more than 210 min, the filtration efficiency of 20 layers of PAN/PE-PP composite filter can be increased to more than 90%, but the resistance also increases sharply, hence the filtration performance of 20 layers of PAN/PE-PP composite filter with electrospinning time of 210 min is the best. Therefore, compared with PAN/PE-PP monolayer composite filter with the same areal density, the filtration performance of PAN/PE-PP multilayer composite filters is obviously improved. The micro-nano fiber multilayer composite method is an effective method to prepare high efficiency and low resistance composite air filters.