Multi-wall carbon nanotube (MWNT), highly textured pyrolytic graphite, necklace-like carbon, and spherical carbon particle were prepared by arc discharge method under atmospheric pressure. These carbon nanomaterials were characterized by field emission scanning electron microscope (FE-SEM), transition electron microscopy (TEM), and Raman spectroscopy. Two-color pyrometry was conducted to measure the temperature of anode surface by high-speed camera. The deposition temperature of MWNT is in the range of 2,400-2,700 K, which indicates that a suitable quenching effect is a necessary condition for the formation of MWNT on the anode surface. The growth mechanism of carbon nanomaterials on the anode surface was estimated, quenching effect playing an important role in the formation of these carbon nanomaterials.