The invention provides a method for preparing gluconic acid by catalytic oxidation and relates to the technical field of biomass efficient transformation and utilization. The gluconic acid is preparedby taking glucose as a raw material and carrying out the catalytic oxidation on Pd/C, wherein a carbon source in a Pd/C catalyst is prepared by carrying out hydrothermal synthesis on the glucose. Onthe basis of a traditional Pd/C catalyst, a traditional activated carbon carrier is replaced with a carbon carrier prepared by taking the glucose as the raw material and carrying out the hydrothermalmethod. A carbon material prepared from a biomass through a hydrothermal method contains more oxygen-containing groups including hydroxyl, carboxyl and the like and has stable metal and capability ofimproving reaction activity, so that the stability and activity of the catalyst are greatly improved; 100 percent conversion rate and 98 percent yield can be reached after the catalyst reacts under normal pressure and room temperature, so that the aim of efficiently preparing the gluconic acid from the glucose under a moderate condition is realized.