Abstract: Coal tar pitch (CTP) was modified either with 10g cinnamaldehyde (CMA) per 100 g CTP, 7 g p-toluene sulfonic acid (PTS) per 100g CTP, or a mixture of 10g CMA and 7 g PTS per 100g CTP. The parent CTP and the modified CTPs were characterized by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis. The four samples were carbonized at different temperatures and the products were characterized by FT-IR and polarized-light microscopy. Results show that the modifications have a large influence on the characteristics and carbonization behavior of the CTP. The distillation of CMA occurs at a temperature lower than 300 ℃ during the carbonization of the CMA-modified CTP. Methyl and methylene groups of the parent CTP and the modified CTPs gradually disappear with increasing temperature during carbonization. The modification of the CTP with the mixture of CME and PTS results in a highest increase (5.08%) of carbonization yield and the most abundant mesophase sphere formation during carbonization