This study presents a novel RSR+STR tandem process for the catalytic oxidation of 2,3,6-trimethylphenol (TMP) to synthesize 2,3,S-trimethyl-1,4-benzoquinone (TMQ) in a gas-liquid liquid three-phase reaction system by combining a rotor-stator reactor (RSR) with a conventional stirred tank reactor (STR). The effects of various operating conditions including rotation speed of the RSR, gas volumetric flow rate, liquid volumetric flow rate, water volume fraction in the liquid phase and reaction temperature on the TMP conversion and TMQ yield were investigated. The TMP conversion and TMQ yield in the RSR+STR tandem process reached 86.9% and 20.0%, respectively, which were much higher than those in the STR process under the same conditions where the conversion and yield were only 46.8% and 6.8% respectively. It is suggested that the improvement of TMQ synthesis in the RSR+STR tandem process is ascribed to the intensification of liquid-liquid mixing, gas-liquid transfer and oxidation reaction in the RSR.