For non-flammability usages, composite structures with nano-additives or carbonized form of polyacrylonitrile (PAN) are generally preferred. In this study, a pre-carbonized form of nanofiber webs (OxPAN) is firstly proposed as a nonflammable material to eliminate the need for carbonization. The thermal oxidative stabilization process is applied to the PAN nanofibers to achieve high structural stability. This prevents melting and fusing during the thermal treatments and thereby improves the thermal stability of the web. PAN nanofiber webs were successfully obtained via the electrospinning technique and the thermal oxidation process was then applied. The structural properties of the oxidized PAN nanofiber webs were investigated by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy, Raman Spectroscopy and X-Ray Photoelectron Spectroscopy and Electrochemical Impedance Spectroscopy. The surface morphology of the OxPAN was examined by scanning electron microscopy and the average fiber diameter was measured as 265 +/- 64 nm. The thermal properties were analyzed with a differential scanning calorimeter and a thermal gravimetric analyzer. The flammability performance was tested via the Limiting Oxygen Index (LOI), and it was found that in addition to being lightweight, OxPAN nanofiber webs exhibit splendid performance with a LOI value of 48-49%.