Abstract: Low-cost jute-based carbon fibers were fabricated by pre-oxidation and carbonization. The chemical, morphological and crystal structure of the jute fibers during pre-oxidation were investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, elemental analysis, X-ray diffraction and scanning electron microscopy. Results show that the optimum pre-oxidation temperature range is from 250 to 340℃. At 250℃, significant oxidation occurs, the amount of C=O functional groups reaches a maximum, the typical cellulose crystal structure disappears and a new aromatic structure appears. The C=O functional groups are gradually lost while an aromatic structure steadily develops with a further increase of temperature from 250 to 340℃. The tensile strength of the jute-based carbon fibers increases with increasing amount of the aromatic structure during pre-oxidation, rather than that of C=O groups. The highest tensile strength of the carbon fibers is （200.4±41.0） MPa.