A surface coating was successfully applied through dipping the polyacrylonitrile (PAN) precursor fibers in a carbon black (CB) bath containing a hydrolyzed binder. The coated fibers were pre-oxidized over the microwave furnace at temperatures ranging from 100 degrees C to 170 degrees C for different heating times. The changes in chemical structure were studied by Fourier transfer infrared spectroscopy combined with elemental analyzer. X-ray diffraction was employed to study the crystalline structure and its related parameters. Differential scanning calorimeter and thermogravimetry were used for thermal analysis. In addition, the fiber morphology and the mechanical properties were also evaluated. Scanning electron microscopy results confirmed the presence of CB on the surface of PAN precursor. The analysis in the chemical structure showed an apparent response of coated PAN fibers to the microwave heating, since the microwave field induced the cyclization and crosslinking reactions. The crystallinity and the crystallite height decreased. Furthermore, the tensile strength and elongation of pre-oxidized fibers decreased with the increase of heating time. The measured oxygen content revealed that the pre-oxidized fibers can withstand the high temperatures on the following stage (carbonization). POLYM. ENG. SCI., 59:457-464, 2019. (c) 2018 Society of Plastics Engineers