. Smooth SAF nanofibers with the average diameter of 236, 340 and 467nm were electrospun at 25kV, using solutions of 11, 13 and 15 wt% SAF/DMF concentration, respectively. Scanning electron Microscopy(SEM) was used to observe and measure the diameters of electrospun nanofibers. In order to prevent nanofibers from relaxing and fix nanofibers length during thermal stabilization, uniaxially aligned nanofibers were collected and fixed by a frame. By comparing FTIR spectrums of thermal stabilized nanofibers and precursors nanofibers, it was observed that stretching peaks of C ? N and C-H functional groups at 2243cm -1 and 2940cm -1 decreased significantly, and then stretching peak of C=N functional group at 1600cm -1 and bending peak of C=C-H functional group at 810 cm -1 appeared. These changes in functional groups of nanofibers, proved accruing of thermal stabilization reactions. Color of the nanofibers changed gradually from white to gold yellow, orange, brown and finally dark brown during thermal stabilization process. By analyzing isothermal DSC spectrums and drawing Avrami curves at 210, 220, 230, 240 and 250 o C, their activation energy were calculated to be -23.15, -23, -20.5, -19.8 and -17.6, respectively. By analyzing the kinetic of the reaction and drawing its Arrhenius’s plot, it was found that the reaction is first order. Extension of reaction(EOR) was calculated by comparing the length of C?N functional group peak with C=N functional group peak at FTIR spectrums. By increasing the stabilization temperature from 170 o C to 230 o C EOR increased from about 0% to 83%. By thermal stabilization of nanofibers at 230 o C for 1 hour and 250 o C for 45 min, EOR increased more than 80%. The EOR of thermally stabilized SAF nanofibers(containing Itaconic acid) and PAN nanofibers(without Itaconic acid) at 230 o C for 1 hour were 83% and 42%, respectively. Pre-treatment of nanofibers by mineral catalyst(KMnO 4 ) at solution’s concentration of 680mg/lit, enhanced extension of thermal stabilization reactions. Diameters of nanofibers decreased from 236nm, 322nm and 467nm to 185nm, 264 and 390nm after thermal stabilization at 230 o C for 1 hour, respectively. The weight of thermally stabilized nanofibers decreased 6.8% and 8% after thermal stabilization at 230 o C and 250 o C for 1 hour, respectively. The enthalpy of thermal stabilization reactions decreased from 507J/g for precursors nanofibers to 135J/g(73% of the primary enthalpy) for thermally stabilized nanofibers. Crystalline index(CI%) and coherent length(L C ) of thermally stabilized nanofibers in different temperatures were measured by WAXD. CI% and L C of heated nanofibers at 170 o C and thermally stabilized nanofibers at temperatures above 190 o C were 60%, 303A? and 35%, 260A?, respectively.