In this research, we compared the discharge characteristics and catalytic efficiency of sulfuric acid, p-toluenesulfonic acid, and their respective sodium salts (sodium sulfate and sodium p-toluenesulfonate) in sawdust liquefaction and found that sulfuric acid was the optimal catalyst when glycerol was used as solvent during the plasma electrolytic liquefaction (PEL) process. When sodium p-toluenesulfonate was used as the only catalyst, the liquefaction yield reached 83.51% after 25 min. This yield was higher than that obtained using sodium sulfate as the catalyst (60.63%) because different concentrations of H ions were produced in PEL. Cellulose, lignin, and holocellulose were extracted from sawdust and successfully liquefied in PEL, illustrating the universality of PEL. The optical emission spectra of the different biomass during the PEL process were similar, indicating that the kinds of free radicals produced were similar, which can accelerate the liquefaction of sawdust.