The issue of deposited carbon (DC) on a reactor wall during the producing of acetylene by the coal/arc plasma process is a potential obstacle for the industrialization process. The formation mechanism of DC is very difficult to reveal because the high complexity of coal sand the volatile matter. Combining with quenching technique, the methane, liquid petroleum gas and benzene were employed as the model materials to roughly act as the light gas, chain and aromatic subcomponents of volatile matter,and then the reasonable formation mechanism of DC was subtly speculated accordingly.