In the present study, a novel process for synthesis of carbon acid catalyst bearing oxygenated groups is proposed based on plasma engineering. The carbon nanoparticles are synthesized with in-situ surface acid modification in a one-pot plasma process with a mixture of carbon precursor and sulfuric acid. The density of total acid groups on the obtained carbon catalyst is up to 3.76–4.42 mmol g−1. The synthesized carbon acid catalysts convert corn cob waste to reducing sugars with the yield of 36.5 % and selectivity of 78.6 % at 180 ℃ for 18 h, respectively. Meanwhile, the stability of carbon acid catalyst in the hydrothermal reaction at 180 ℃ was examined via concessive runs and the recyclability can be maintained at 77.6 % after three times utilization. This process is superior to the conventional methods in the aspects of simplified operation, mild condition, and high efficiency by integrating the carbon synthesis and surface functionalization. The comparable catalytic performance of the resulting carbon acid catalyst provides new guidance to design of solid acid catalysts based on plasma engineering for biomass transformation.