Abstract: The microstructure of micro-coiled carbon fibers synthesized by the catalytic decomposition of acetylene was analyzed using scanning electron microscopy, Raman spectroscopy, X-ray diffraction, thermogravimetry and nitrogen cryo-adsorption and compared with those of straight carbon fibers with a similar diameter. The crystalline sizes of the graphitic domains of the straight carbon fibers are larger than those of the micro-coiled fibers, but the outer layers of the micro-coiled carbon fibers are more ordered than that of the straight carbon fibers. The pore size distribution of straight carbon fibers is broad, while the pore size of the micro-coiled carbon fibers is narrowly distributed between 3nm and 4nm. The pore volume of micro-coiled carbon fibers is much higher than that of straight carbon fibers, and its BET surface area is almost ten times as much as that of straight carbon fibers. Results show that the oxidation resistance, hydrogen storage and electrochemical capacitance of the micro-coiled carbon fibers are superior to those of straight carbon fibers.