Bag filters are generally used to remove particulate matter from the dust-laden flue gas exhausted from cornbustors. Recently, great effort has been expended to improve the performance of bag filters by coating the filter surface with nanofibers. In this study, meta-aramid nanofibers with high thermal durability were produced by an electrospinning process, and the effect of fiber diameter on the filter quality factor was theoretically and experimentally investigated. Electrospun filters with mean fiber sizes of 333 nm and 569 nm were successfully prepared by controlling the electrospinning parameters. The filters had high mechanical and chemical durability, as per the results of thermogravimetric analyzer (TGA), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), and a tensile strength analyses. In addition, the particle collection efficiency and pressure drop of the filters increased as the fiber diameter decreased. The filter quality factor, determined by the relationship between the collection efficiency and the pressure drop, increased slightly with the decrease in fiber diameter, although the experimental results were slightly different from the theoretical results.