The microstructure evolution of phenolic fibers carbonized at different temperatures and the influence of the resulting microstructure on the mechanical and electrical behaviors were investigated using a combination of techniques including thermogravimetric analysis-mass spectroscopy (TG-MS), Fourier transform infrared spectroscopy (FT-IR), laser Raman spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), N 2 physical adsorption, tensile strength and electrical conductivity measurements. The results showed that below 500 โข C aromatic union was crosslinked by aliphatic bridges; above 500 โข C with increasing temperature the polymer network was destroyed, hexagonal carbon layers were gradually formed; above 850 โข C the content of the hexagonal carbon layers was further increased due to the transformation of the amorphous carbons in the fibers; above 1500 โข C slow evolution toward ideal graphite was occurred. The accessible micropores (<1.2 nm, 200-1040 m 2 /g) could be detected in the range of 600-950 โข C. The tensile strength of the carbon fibers exhibited a maximum value of 640 MPa at 550 โข C. The electric conductivity increased with increasing temperature and reached a maximum value of 2.45 ร 10 4 S/m at 2800 โข C.