Abstract: Proposed is a method of preparing glucaric acid from glucose through TEMPO oxidation. The method of preparing glucaric acid includes (a) reacting glucose in a solvent through an oxidation reaction using 4-acetamido-TEMPO serving as a nitroxide radical-mediated organocatalyst, potassium bromide serving as a co-catalyst, and potassium hypochlorite serving as an oxidizing agent to prepare glucaric acid. The method can improve the conversion efficiency of glucose to glucaric acid through optimal conditions of the temperature, pH, and input of the oxidizing agent in an oxidation reaction using a TEMPO acid catalyst.