The kinetics of ρ-toluene sulfonic acid (PTSA)-catalyzed cellulose liquefaction in the presence of phenol were investigated at 130, 140 and 150 ℃. The resulting liquefied products were also analyzed to evaluate the effectiveness of PTSA as a catalyst during the phenol liquefaction. The liquefaction rate of PTSA was slightly lower than that of sulfuric acid (SA), which was used as a reference catalyst, at each liquefaction temperature. The activation energies of the PTSA and SA catalysts during the phenol liquefaction of cellulose calculated using the Arrhenius equation were 34.5 and 35.5 kcal/mol, respectively. The chemical compositions of the ether extracts in the liquefied products were very similar to both catalysts. Methylene bisphenol and its isomers, which were the primary components in the ether extracts, comprise approximately 30% of the ether extract. The GPC curves of the 80% dioxane-soluble part of the liquefied product indicated that it consists of a remarkable amount of phenol-based trimers to hexomers. The average molecular weight and the polydispersity of the liquefied products were very similar after liquefaction using both catalysts; therefore, differences in the products produced using both catalysts used were not recognized. However the level of combined phenol in the liquefied product produced using the PTSA catalystwas approximately 50% lower than that of the SA catalyst. Although it is believed that this difference may cause retardation of the rate of liquefaction, further experiments are necessary to explain differences in the effectiveness of organic sulfonic acid catalysts during the phenol liquefaction of lignocellulosic biomass.