The polyimide precursor (polyamic acid) produced of 4, 4'-oxydiphthalic anhydride and 4, 4'-oxydianiline was electrospun using needleless electrospinning method. Nonwoven layers consisting of submicron fibers with diameters in the range about 143-470 nm on the polypropylene spunbond supporting web were produced. Filtration properties of these nanofiber layers on the highly permeable polypropylene support-namely filtration effectivity and pressure drop-were evaluated. Consequently, these polyamic acid fibers were heated to receive polyimide nanofibers. The imidization process has been studied using IR spectroscopy. Some comparisons with the chemically identical polyimide prepared as the film were made.