Partially aligned and oriented polyacrylonitrile (PAN) nanofibers were electrospun from PAN Solution in dimethylformamide (DMF) for the preparation of carbon nanofibers. The as-spun polyacrylonitrile nanofibers were hot-stretched by weighing metal in a temperature controlled oven to improve its crystallinity and molecular orientation. Then they were stabilized at 250 degrees C under stress, and carbonized at 1000 degrees C in N(2) atmosphere by fixing the length of the stabilized nanofibers to convert them into carbon nanofibers. The result showed that the average diameter of the carbon nanofibers was 140 mu. The degree of crystallinity of the stretched fibers confirmed by X-ray diffraction analysis was enhanced 4-fold in comparison with that of as-spun fibers. The improved fiber alignment and crystallinity resulted in the increased modulus and tensile strength of the nanofibers as much as 5.7-fold and 4.7-fold, respectively. The modulus and tensile strength the of carbon nanofiber increased up to 2243 +/- 120 MPa and 170 +/- 15.8 GPa, respectively. Thus, the hot-stretched nanofiber can be used as a potential precursor to produce high-performance carbon composites.