Biomass resources in nature produce a large amount of waste resources (agricultural residues, wood waste, etc.) during agricultural and forestry production processes. Therefore, the effective utilization of these solid biomass waste resources has attracted widespread interest. In this paper, a pulsed discharge plasma technology was used to perform catalytic liquefaction experiments on solid biomass sawdust at room temperature and atmospheric pressure, and the reaction parameters such as the solid:liquid ratio, liquefaction solvent ratio, and catalyst ratio were optimized. The results showed that the plasma technology achieved a higher liquefaction yield; the optimized reaction parameters were: a solid:liquid ratio of 1:23.4, a liquefaction solvent polyethylene glycol (PEG) / glycerol (GL) ratio of 25:15 (V:V), and an acid volume fraction of 0.188%. In addition, the characteristics of the products of the liquefaction reaction were analyzed and discussed. The liquid products were mainly composed of small molecules. The experiment established that the liquefaction of solid sawdust by high-voltage pulsed discharge plasma can be an effective technical method.