We investigated the discharge characteristics, parameters, water content, and mechanism of liquefying biomass by plasma electrolysis under alkaline conditions. Compared with the liquefaction of sawdust under acidic conditions, the discharge changed from corona to spark discharge, the liquefaction time was a little longer (8 min), and the pondus Hydrogenii (pH) of the bio-oil was 7.54 under sodium hydroxide catalyst. We identified the optimal parameters for sawdust liquefaction by sodium hydroxide, sodium carbonate, and sodium bicarbonate using a single factor method and found that the optimal parameters for sodium hydroxide and carbonate were quite different, apparently because they have different liquefaction mechanisms. When the water content increased, the liquefaction rate remained constant, so the water content prolonged the treatment time but did not affect the liquefaction rate or product quality. To analyze the universality of liquefied cellulose biomass under alkaline conditions, corn cob, rice straw, and cotton were liquefied separately. We found that the liquefaction time increased significantly with an increase in cellulose content. Notably, plasma electrolytic liquefaction efficiently heated the solution and effectively catalyzed the liquefaction of biomass with high energy efficiency, making this a promising biomass conversion technology. (C) 2020 Elsevier Ltd. All rights reserved.