This paper reports the effect of the conditions of stabilization process on the properties of special polyacrylonitrile nanofibers (SAF) with an average diameter of 467 nm. Stabilization constitutes an important pretreatment for the production of either carbon fibers or activated carbon fibers. It was found that the higher the stabilization temperature, the lower the initial induction time and the total reaction time. Extent of reaction increases with both treatment time and temperature of stabilization process. Crystallinity index and crystal size of stabilized nanofibers decreases as a result of stabilization. Special polyacrylonitrile nanofibers containing itaconic acid shows a higher capability for stabilization process. Potassium permanganate as a catalyst leaves a positive effect on the extent of reaction of stabilization. The diameter of nanofibers decreases by about 20% as a result of stabilization at 250 °C. Thermally stabilized nanofiber shows a wider exothermic peak with a lower height.